Add some handy settings to posts view.

Extract similar behavior of posts view settings and jump to page view into the
AwfulSemiModalViewController. AwfulSettings needed a way for callers to extract
appropriate minimum and maximum values for a given setting; this could be
formalized.

Closes #188
Clear *all* cookies when logging out.
Don't remove pull-to-refresh view when scroll view leaves.

The actual fix is the removal of -[UIScrollView(SVPullToRefresh)
willMoveToSuperview:], a questionable override of a UIKit class's instance
method. The code from AwfulThreadListController was simply dead code.

Fixes #193
Fix spurious errors building CSS.
Inconsequential CSS formatting changes.

No idea why these changed.