Adds liniting into the workflow (#3082)

* initial linting of src

* fix indent to 2 spaces

* Removes unnecessary rules

* ignore spec folder for now

* Spec linting

* Fix spec indent

* nits

* nits

* no no-empty rule

spec/SessionTokenCache.spec.js

@@ -17,7 +17,7 @@ describe('SessionTokenCache', function() {
   it('can get undefined userId', function(done) {
     var sessionTokenCache = new SessionTokenCache();
 
-    sessionTokenCache.getUserId(undefined).then((userIdFromCache) => {
+    sessionTokenCache.getUserId(undefined).then(() => {
     }, (error) => {
       expect(error).not.toBeNull();
       done();