Fix the call te git_commit_create in GTCommit.m which was causing the tests to break

When updating for the new libgit2 API this method was rewritten but the parameters for the message and message_encoding were flipped.

Turned them round the correct way and the Mac OS tests now work on master.
don't leave extra new lines in the message
Merge branch 'master' into arc
Merge remote-tracking branch 'origin/master'
Merge pull request #37 from Abizern/fix_GCCommit

Fix the call te git_commit_create in GTCommit.m which was causing the tes
Merge branch 'master' into arc
Removed old references to libgit2
Re-added libgit2 as a submodule.
Added libgit2-ios static library target, made ObjectiveGit-iOS pseudo-framework.
OS X framework target now uses libgit2 static target too.
Fixed iOS tests target. Also, iOS does not support garbage collection.
Added missing public header to iOS framework target.
This script for iOS is no longer needed.
Updated README with new submodule and iOS instructions.
libgit2 targets shouldn't complain about unused values.
Reinstated -[GTCommit shortMessage]
Revert "Remove test for 'shortMessage' which has been removed from the API"

I've brought -[GTCommit shortMessage] back into the fold. :)
-[GTCommit shortMessage] has been renamed to -[GTCommit messageTitle] by popular demand.
Merge branch 'master' into shortmessage
Add instructions ObjectiveGit linking with desktop applications

Also linked with an example of how this has been done.