Bug 1087314 - Preserve visible UI whitespace in grunt builds

This work fixes Bugzilla bug [1087314](https://bugzilla.mozilla.org/show_bug.cgi?id=1087314).

In it we prevent grunt minification from stripping trailing white space in the markup, observed in `result-set-title-left` in the "-".

Here's the before and after:

![resultsettitleleftcurrent](https://cloud.githubusercontent.com/assets/3660661/4780749/a30f1fe8-5c76-11e4-8fec-331933af74cd.jpg)

![resultsettitleleftproposed](https://cloud.githubusercontent.com/assets/3660661/4780750/a551f2ee-5c76-11e4-8162-97541a0b10f3.jpg)

I chose to make the change for only `treeherder:` and not `logviewer:`, in the Gruntfile, since logviewer didn't contain any known issues.

nb. I noticed my filters lost their white space separation in my local grunt dist, but I checked with a rebuild of master and it was the same (so I think that is just some oddity of viewing the index locally, not through a server).

Tested on Windows:
FF Release **33.0**
Chrome Latest Release **38.0.2125.104 m**

Adding @camd for review and @edmorley for visibility.