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:

```js
var _, Backbone, BaseModel;

_ = require('underscore');
Backbone = require('backbone');
BaseModel = require('../shared/base/model');
```

After:

```js
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'm using comma-first, semi-colon on
newline style for these because I find it makes diffs easier when
dependencies change.