🌈 sessions were re-written, update to 4.0.0-alpha.2, read HISTORY.md

**Sessions were re-written **

- Developers can use more than one 'session database', at the same time,
to store the sessions
- Easy to develop a custom session database (only two functions are
required (Load & Update)), [learn
more](https://github.com/iris-contrib/sessiondb/blob/master/redis/database.go)
- Session databases are located
[here](https://github.com/iris-contrib/sessiondb), contributions are
welcome
- The only frontend deleted 'thing' is the: **config.Sessions.Provider**
- No need to register a database, the sessions works out-of-the-box
- No frontend/API changes except the
`context.Session().Set/Delete/Clear`, they doesn't return errors
anymore, btw they (errors) were always nil :)
- Examples (master branch) were updated.

```sh
$ go get github.com/iris-contrib/sessiondb/$DATABASE
```

```go
db := $DATABASE.New(configurationHere{})
iris.UseSessionDB(db)
```

> Note: Book is not updated yet, examples are up-to-date as always.

config/sessions.go

@@ -17,50 +17,18 @@ const (
 	DefaultCookieName = "irissessionid"
 	// DefaultSessionGcDuration  is the default Session Manager's GCDuration , which is 2 hours
 	DefaultSessionGcDuration = time.Duration(2) * time.Hour
-	// DefaultRedisNetwork the redis network option, "tcp"
-	DefaultRedisNetwork = "tcp"
-	// DefaultRedisAddr the redis address option, "127.0.0.1:6379"
-	DefaultRedisAddr = "127.0.0.1:6379"
-	// DefaultRedisIdleTimeout the redis idle timeout option, time.Duration(5) * time.Minute
-	DefaultRedisIdleTimeout = time.Duration(5) * time.Minute
-	// DefaultRedisMaxAgeSeconds the redis storage last parameter (SETEX), 31556926.0 (1 year)
-	DefaultRedisMaxAgeSeconds = 31556926.0 //1 year
-
 )
 
 type (
 
-	// Redis the redis configuration used inside sessions
-	Redis struct {
-		// Network "tcp"
-		Network string
-		// Addr "127.0.0.1:6379"
-		Addr string
-		// Password string .If no password then no 'AUTH'. Default ""
-		Password string
-		// If Database is empty "" then no 'SELECT'. Default ""
-		Database string
-		// MaxIdle 0 no limit
-		MaxIdle int
-		// MaxActive 0 no limit
-		MaxActive int
-		// IdleTimeout  time.Duration(5) * time.Minute
-		IdleTimeout time.Duration
-		// Prefix "myprefix-for-this-website". Default ""
-		Prefix string
-		// MaxAgeSeconds how much long the redis should keep the session in seconds. Default 31556926.0 (1 year)
-		MaxAgeSeconds int
-	}
-
 	// Sessions the configuration for sessions
-	// has 4 fields
-	// first is the providerName (string) ["memory","redis"]
-	// second is the cookieName, the session's name (string) ["mysessionsecretcookieid"]
+	// has 5 fields
+	// first is the cookieName, the session's name (string) ["mysessionsecretcookieid"]
+	// second enable if you want to decode the cookie's key also
 	// third is the time which the client's cookie expires
 	// forth is the gcDuration (time.Duration) when this time passes it removes the unused sessions from the memory until the user come back
+	// fifth is the DisableSubdomainPersistence which you can set it to true in order dissallow your iris subdomains to have access to the session cook
 	Sessions struct {
-		// Provider string, usage iris.Config().Provider = "memory" or "redis". If you wan to customize redis then import the package, and change it's config
-		Provider string
 		// Cookie string, the session's client cookie name, for example: "irissessionid"
 		Cookie string
 		// DecodeCookie set it to true to decode the cookie key with base64 URLEncoding
@@ -75,7 +43,7 @@ type (
 		// Default 2 hours
 		GcDuration time.Duration
 
-		// DisableSubdomainPersistence set it to dissallow your iris subdomains to have access to the session cookie
+		// DisableSubdomainPersistence set it to true in order dissallow your iris subdomains to have access to the session cookie
 		// defaults to false
 		DisableSubdomainPersistence bool
 	}
@@ -84,7 +52,6 @@ type (
 // DefaultSessions the default configs for Sessions
 func DefaultSessions() Sessions {
 	return Sessions{
-		Provider:                    "memory", // the default provider is "memory", if you set it to ""  means that sessions are disabled.
 		Cookie:                      DefaultCookieName,
 		DecodeCookie:                false,
 		Expires:                     CookieExpireNever,
@@ -115,41 +82,3 @@ func (c Sessions) MergeSingle(cfg Sessions) (config Sessions) {
 
 	return
 }
-
-// DefaultRedis returns the default configuration for Redis service
-func DefaultRedis() Redis {
-	return Redis{
-		Network:       DefaultRedisNetwork,
-		Addr:          DefaultRedisAddr,
-		Password:      "",
-		Database:      "",
-		MaxIdle:       0,
-		MaxActive:     0,
-		IdleTimeout:   DefaultRedisIdleTimeout,
-		Prefix:        "",
-		MaxAgeSeconds: DefaultRedisMaxAgeSeconds,
-	}
-}
-
-// Merge merges the default with the given config and returns the result
-func (c Redis) Merge(cfg []Redis) (config Redis) {
-
-	if len(cfg) > 0 {
-		config = cfg[0]
-		mergo.Merge(&config, c)
-	} else {
-		_default := c
-		config = _default
-	}
-
-	return
-}
-
-// MergeSingle merges the default with the given config and returns the result
-func (c Redis) MergeSingle(cfg Redis) (config Redis) {
-
-	config = cfg
-	mergo.Merge(&config, c)
-
-	return
-}