Convert Token from enum to struct (#256)

* convert Token from enum to struct

* private setter for components

* updated CHANGELOG

Sources/ForTag.swift

@@ -9,7 +9,7 @@ class ForNode : NodeType {
   let token: Token?
 
   class func parse(_ parser:TokenParser, token:Token) throws -> NodeType {
-    let components = token.components()
+    let components = token.components
 
     func hasToken(_ token: String, at index: Int) -> Bool {
       return components.count > (index + 1) && components[index] == token