Don't package the Rakefile nor the test files when building a gem.
There is no `man` directory.
Include the libgit2 AUTHORS and COPYING files.
Merge pull request #263 from libgit2/stop-bundling-tests

Don't package the Rakefile nor the test files when building a gem.
Fix an issue with Rugged::Object#lookup not honoring the object type.

Subclasses of Rugged::Object should only be able to look up objects of
their type, but were returning any object type.
Make sure subclasses are handled correctly.
Only loop over ancestors if necessary.
Also add tests for subclasses of Rugged::Object.
Merge pull request #264 from arthurschreiber/fix-lookup

Fix an issue with Rugged::Object#lookup not honoring the object type.
Simplify the way inheritance is checked.

Thanks @nvloff!
Fix a reference to Rugged::Repository.init_at method
Merge pull request #265 from mmozuras/fix_reference_to_repository_init_at

Fix a reference to Rugged::Repository.init_at method
Don't require rubygems.
Remove a 1.8 <> 1.9 shim.