Behavior specs cleanup: Move spec/api/generated-parser-behavior.spec.js

Move spec/api/generated-parser-behavior.spec.js to
spec/behavior/generated-parser-behavior.spec.js. It's not an API test,
strictly speaking.

spec/index.html

@@ -16,7 +16,7 @@
     <script src="api/pegjs-api.spec.js"></script>
     <script src="api/plugin-api.spec.js"></script>
     <script src="api/generated-parser-api.spec.js"></script>
-    <script src="api/generated-parser-behavior.spec.js"></script>
+    <script src="behavior/generated-parser-behavior.spec.js"></script>
     <script>
       (function() {
         var env      = jasmine.getEnv(),