Added some documentation.
Removed +[GitLooseStorage atomicallyWriteData:toFileAtURL:]

This method contained a custom atomic-write algorithm, ported directly
from the Ruby original. GitLooseStorage now uses the Cocoa atomic-write
methods.
Formatting cleanup.
Improved error reporting.

+[GitLooseStorage unpackObjectHeader:objectType:size:bytesUsed:] no
longer fails silently when fed a NULL output pointer.