Update instruction comments in application.js
Pass size of 60px to gravatar function from navbar. Since it won't be larger than that, no point loading a larger 200px image and then shrinking it. 60px already takes into consideration retina displays. The actual size of avatar is 30px.
Refactor gravatar function
Remove mongoose reference
Update Contributing section
Update jsdoc strings
Merge remote-tracking branch 'origin/master'

* origin/master:
  Added Express tutorial link