Fixed joining networks from networks list pages

WIP #39
https://assemblymade.com/coderwall/wips/39

Networks cannot be joined in production due to an improperly formed href value on the Join button/link.

* Removed improper caching from networks/_alphabetized_list partials.
* Also adjusted the width of the header for aesthetics on networks list pages

Caching of the _alphabetized_list partial would cache and display improper html that was inappropriate for logged in users vs non logged in users.  This causes joining a network to be broken currently for logged in users.

I have removed the caching entirely from the partial for 2 reasons:
* There are ~70 Networks at the moment, so caching is not entirely necessary at the moment.
* The controller action is pulling Network.all from cache anyways.  Caching the sorted partial seems overkill right now, especially considering it's breaking Join/Leave in production


I also took the opportunity to widen the navigation header in the Networks list pages, I think it looks better:

Before:
![networks-header](https://cloud.githubusercontent.com/assets/197892/3402344/e15c62c2-fd5a-11e3-9b23-db40e79ddaa5.png)

After:
![networks-full-width](https://cloud.githubusercontent.com/assets/197892/3402349/e6aacd2c-fd5a-11e3-947b-c50dc9f9cf67.png)