Skip failling tests due to recent github handling modification of include-tag

Github recently (25th of december, 2013) changed its handling of the include-tag option. Skipping tests while waiting for a proper solution to be found.

Same thing as libgit2/libgit2#2020
Delegate Commit.MessageShort to libgit2 (#593)
Add failing test
Update test coverage

Cover deletion and tree-to-tree diffs
Remarshal and rename flags
Add git_patch bindings and fix patch generation
Use InAttribute on callbacks
Stop checking config for signatures