Add SWTableViewCell pod.
Remove threadImage and update UI for TSMessageThreadCell.
Make TSMessageThreadCell a subclass of SWTableViewCell.
Implement delete button on message thread view controller.

- Also animates the the bar button items when entering/exiting editing mode
pods
testing out ui-improvments FREEBIE

Merge branch 'ui-improvements' of https://github.com/ursachec/TextSecure-iOS into ursachec-ui-improvements