Js improvements

Fixes #281 and fixes #273

- Adds fastclick
- Move customer js to the bottom of the page
- Move comment hash JS helpers to Timber's `shop.js`
- Move login/recover password JS to Timber's `shop.js`

Demo shop for new updates - http://steve-dev.myshopify.com/

@stevebosworth @mpiotrowicz 
Take another look at the JS file and [this line](https://github.com/Shopify/Timber/pull/296/files#diff-cd3c9dd5e1127d7a0bd0bd272520dcc5R178). I set a global variable inline, and then that is checked in `shop.js`.

- Set `timber.global` object inline (article page for comments and reset password flag)
  - This can't be a liquid variable instead since they aren't transferred between templates/assets
- No duplicate calls to `cacheSelectors`
- Extend `timber.globalVars` into `timber.global`, which may already be set

Any up/downsides to extending this way? Are the names obvious enough, with a bit of documentation?