Js improvements

Fixes #281 and fixes #273

- Adds fastclick
- Move customer js to the bottom of the page
- Moved Modernizr to bottom of page
  - This is not recommended with IE8 support still on the table because of the HTML5 shiv, but we load that conditionally at the top of the page in `oldIE-js.liquid` rather than as a part of Modernizr
- Move comment hash JS helpers to Timber's `shop.js`
- Move login/recover password JS to Timber's `shop.js`

@stevebosworth @mpiotrowicz 
Thoughts on this approach? This is called from `login.liquid` before `timber.init()` so the cached selectors won't exist yet. This checks if they exist (which we assume they don't) and gets them ready.