Complete Refactor

Currently, SMSTimestamps won't work properly with an iPad (oldDate unreliably gets set to nil). This version will work with iOS from 3.0 to the latest, on iPhone and iPad (and I'm assuming iPods...).

Also adds the option to chop seconds from calculating time differences (similar to Apple's implementation). That'll make it so if a text comes in at 1:01:30 and you reply at 1:02:10, a timestamp will appear (if the setting is set to 1 minute).

This also removes .DS_Stores. Their useless file generated by Finder.