Sweep codebase for style tweaks

In a fit of OCD, I went through the source files to standardize some
stylistic formatting. Most changes are to the `var` declarations at the
top of files. I.e., before:

    var _, Backbone, BaseModel;

    _ = require('underscore');
    Backbone = require('backbone');
    BaseModel = require('../shared/base/model');

After:

    var _ = require('underscore'),
        Backbone = require('backbone'),
        BaseModel = require('../shared/base/model');

The original style of declaring `var` first was cruft leftover from the
original CoffeeScript codebase.

I also do a sweep of comment formatting for consistency.
Merge pull request #231 from airbnb/style-tweaks

Sweep codebase for style tweaks