fixed typos, added error prefix and added usage to README.md

token.go

@@ -8,7 +8,7 @@ import (
 	"strings"
 )
 
-// Token is the JWT token representation
+// Token represents a JWT token
 type Token struct {
 	raw          string
 	data         string
@@ -23,17 +23,17 @@ func (t *Token) String() string {
 	return t.raw
 }
 
-// Sig returns the Tokens URLEncoded signature
+// Sig returns the tokens URLEncoded signature
 func (t *Token) Sig() string {
 	return t.signature
 }
 
-// RawSig returns the Tokens raw signature
+// RawSig returns the tokens raw signature
 func (t *Token) RawSig() []byte {
 	return t.rawSignature
 }
 
-// Data returns the first two token fields
+// Data returns the first two URLEncoded token fields
 func (t *Token) Data() string {
 	return t.data
 }