Make sign-in page responsive

Kick off our 'responsive' branch with
a quick take of the sign-in page.
Make header and footer responsive
Admin: Limit visibility to non-xs screens

We can make this nice later.
Profile: Limit visibility to non-xs screens

This is a lame workaround, but we'll get back
to it after the backlog is responsive.
Refactor: Backlog: Put col-md classes everywhere

Put col-md-* classes everywhere there is a col-xs-*
class, as we prepare to look differently on smaller
screens.
Backlog: Look reasonable on iPhone, no selections

Make the story list look reasonable. The story
details will be updated in a later commit.
Backlog: Selected story looks reasonable on iPhone

Also now 'my' stories have blue text.
Make the archives responsive
Fix: Backlog: isStoryMine check for undefined
Fix: Hide menu when not signed in

The visibility stuff with Bootstrap
and Angular don't mix very well. Use
ng-if instead of ng-show to get what
we're going for.
Put a max width on the top-level container

Let's go with 1350px for now.
Version 0.6.4

This release is ready to be used by friends.

Since 0.6.3:

 * Basic responsive design
 * Stability improvements on server
 * Stability improvements on client
 * Sad / stopped stories

 :-)