Convert Token from enum to struct (#256)

* convert Token from enum to struct

* private setter for components

* updated CHANGELOG

Sources/Include.swift

@@ -7,7 +7,7 @@ class IncludeNode : NodeType {
   let token: Token?
 
   class func parse(_ parser: TokenParser, token: Token) throws -> NodeType {
-    let bits = token.components()
+    let bits = token.components
 
     guard bits.count == 2 || bits.count == 3 else {
       throw TemplateSyntaxError("""