Improve sync method. Improve docs.

README.md

@@ -8,6 +8,7 @@ GNU gettext utilities for Go.
 - It works with UTF-8 encoding as it's the default for Go language. 
 - Supports pluralization rules.
 - Ready to use inside Go templates.
+- Safe for concurrent use accross multiple goroutines.
 - Language codes are automatically simplified from the form "en_UK" to "en" if the formed isn't available.
 - Unit tests available
 
@@ -34,6 +35,38 @@ Refer to the Godoc package documentation at (https://godoc.org/github.com/leonel
 
 
 
+# About translation function names
+
+The standard GNU gettext defines helper functions that maps to the gettext() function and it's widely adopted by most implementations. 
+
+The basic translation function is usually _() in the form: 
+
+```
+_("Translate this")
+``` 
+
+In Go, this can't be implemented by a reusable package as the function name has to start with a capital letter in order to be exported. 
+
+Each implementation of this package can declare this helper functions inside their own packages if this function naming are desired/needed: 
+
+```go
+package main
+
+import "github.com/leonelquinteros/gotext"
+
+func _(str string, vars ...interface{}) string {
+    return gotext.Get(str, vars...)
+}
+
+``` 
+
+This is valid and can be used within a package.
+
+In normal conditions the Go compiler will optimize the calls to _() by replacing its content in place of the function call to reduce the function calling overhead. 
+This is a normal Go compiler behaviour.  
+
+
+
 # Usage examples
 
 ## Using package for single language/domain settings