Added failing test for millisecond precision support.
Added Xcode implicit workspace, ignore user data.
Support parsing of dates with millisecond accuracy.

NSDateComponents doesn't support fractional seconds, but we can still
add the extracted milliseconds to the parsed date afterwards.
Corrected the accuracy parameter to STAssertEqualsWithAccuracy.
Clarified that this is a fraction of a second, not a whole number of milliseconds. Also some style consistency fixes.
Merge branch 'support-millisecond-precision' from lukeredpath's fork, with a couple of fixes from me.