Resovles #95, adds ADL.activityTypes object

Implemented per ADL.verbs with the list taken from here: http://xapi.vocab.pub/datasets/adl/

Gruntfile.js

@@ -17,6 +17,7 @@ module.exports = function(grunt) {
         files: {
           'dist/xapiwrapper.min.js': [
             'lib/cryptojs_v3.1.2.js',
+            'src/activitytypes.js',
             'src/verbs.js',
             'src/xapiwrapper.js',
             'src/xapistatement.js',

src/activitytypes.js

@@ -0,0 +1,19 @@
+(function(ADL){
+   ADL.activityTypes = {
+      "assessment": "http://adlnet.gov/expapi/activities/assessment",
+      "attempt": "http://adlnet.gov/expapi/activities/attempt",
+      "course": "http://adlnet.gov/expapi/activities/course",
+      "file": "http://adlnet.gov/expapi/activities/file",
+      "interaction": "http://adlnet.gov/expapi/activities/interaction",
+      "lesson": "http://adlnet.gov/expapi/activities/lesson",
+      "link": "http://adlnet.gov/expapi/activities/link",
+      "media": "http://adlnet.gov/expapi/activities/media",
+      "meeting": "http://adlnet.gov/expapi/activities/meeting",
+      "module": "http://adlnet.gov/expapi/activities/module",
+      "objective": "http://adlnet.gov/expapi/activities/objective",
+      "performance": "http://adlnet.gov/expapi/activities/performance",
+      "profile": "http://adlnet.gov/expapi/activities/profile",
+      "question": "http://adlnet.gov/expapi/activities/question",
+      "simulation": "http://adlnet.gov/expapi/activities/simulation"
+   };
+}(window.ADL = window.ADL || {}));