Updated StatHat tracking for SMS games

#### What's this PR do?
This updates our StatHat reporting for SMS games. We should effectively be able to track:
- total number of people who create and are invited to a game
- total number of people who make it to the start of a game
- total number of people who make it to the end of a level (+ distinguish between alpha and beta users)
- total number of people who make it to the end of a game (+ distinguish between alpha and beta users)
- total number of alpha players who end up playing solo

#### Where should the reviewer start?
PR #318 makes `app` a global var, and so does this.

###### SGCompetitiveStoryController.js
I created some StatHat wrapper functions `stathatReportCount/Value` to standardize the way stat names would be created. I basically took it from Google Analytics event model: category - action - label. I'm also including the `storyId` so that we can distinguish between alpha and beta variants of our SMS games.

#### How should this be manually tested?
I manually ran through a two person game from start to finish.

#### What are the relevant tickets?
Closes #238