feat(state): Expose the internal state API via $$state()

Closes #13

Author: christopherthielen

src/state/interface.ts

@@ -127,6 +127,13 @@ export interface StateDeclaration {
    * ```
    */
   parent?: (string|StateDeclaration);
+  
+  /** 
+   * Gets the private API portion of the state
+   * 
+   * @hidden 
+   */
+  $$state?: () => State;
 
   /**
    * A property of [[StateDeclaration]]:

src/state/stateBuilder.ts

@@ -53,6 +53,11 @@ export class StateBuilder {
     const root = () => matcher.find("");
 
     this.builders = {
+      self: [function (state: State) {
+        state.self.$$state = () => state;
+        return state.self;
+      }],
+
       parent: [function (state: State) {
         if (isRoot(state)) return null;
         return matcher.find(self.parentName(state)) || root();