stathatReport scoping fix

#### What's this PR do?
Within Tips.js, this.app was undefined and the this.app.stathatReport function was breaking. Found out that this was because of 'this' scoping issues within the Mongoose query callback. Fixed by assigning self = this. 

#### How should this be manually tested?
Post to ds/tips and verify that this works. 

#### What are the relevant tickets?
Fixes #116