Upgrade to new go errors and some minor fixes and improvements including easier debugging of invalid routes and e.t.c.

Former-commit-id: 5809157b952ccc61a67a9861470774b3a6fee024

view/jet.go

@@ -47,6 +47,10 @@ var jetExtensions = [...]string{
 
 // Jet creates and returns a new jet view engine.
 func Jet(directory, extension string) *JetEngine {
+	// if _, err := os.Stat(directory); os.IsNotExist(err) {
+	// 	panic(err)
+	// }
+
 	extOK := false
 	for _, ext := range jetExtensions {
 		if ext == extension {