Latest changes from GitHub, and bundler 

This pulls all the changes from the vendored version in github/github, pulls in the changes from #1 and https://github.com/mojombo/grit/pull/180 to attempt to get the tests passing.  There are still 3 failures on Ruby 2.0:

```
$ bx rake
/opt/boxen/rbenv/versions/2.0.0-github6/bin/ruby -I"lib:lib:test:." -I"/opt/boxen/rbenv/versions/2.0.0-github6/lib/ruby/gems/2.0.0/gems/rake-10.1.1/lib" "/opt/boxen/rbenv/versions/2.0.0-github6/lib/ruby/gems/2.0.0/gems/rake-10.1.1/lib/rake/rake_test_loader.rb" "test/**/test_*.rb" 

*** Mocha deprecation warning: Change `require 'mocha'` to `require 'mocha/setup'`.

test/unit warning: method TestRepo#test_diff is redefined
Run options: 

# Running tests:

[ 32/210] TestCommit#test_list_from_string_with_single_signed_commitunknown header 'mergetag' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
[ 62/210] TestGit#test_piping_should_work_on_1_9 = 0.01 s                                 
  1) Failure:
test_piping_should_work_on_1_9(TestGit) [/Users/brandon/github/grit/test/test_git.rb:91]:
not all expectations were satisfied
unsatisfied expectations:
- expected exactly once, not yet invoked: #<Grit::Git:0x1041b5080>.sh('/opt/boxen/homebrew/bin/git --git-dir='/Users/brandon/github/grit/test/..' archive 'master' | gzip')


[100/210] TestRepo#test_alternates_setter_ok = 0.00 s                                    
  2) Failure:
test_alternates_setter_ok(TestRepo) [/Users/brandon/github/grit/lib/grit/git.rb:112]:
unexpected invocation: File.exist?('/Users/brandon/github/grit/.git/.')
unsatisfied expectations:
- expected exactly once, not yet invoked: #<AnyInstance:File>.write('/path/to/repo.git/objects\n/path/to/repo2.git/objects')
satisfied expectations:
- expected exactly once, invoked once: File.exist?('/path/to/repo2.git/objects')
- expected exactly once, invoked once: File.exist?('/path/to/repo.git/objects')


[139/210] TestRevListParser#test_parsing_single_commitunknown header 'mergetag' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
unknown header '' in commit 671d0b0a85af271395eb71ff91f942f54681b144
 = 0.02 s
  3) Failure:
test_parsing_single_commit(TestRevListParser) [/Users/brandon/github/grit/test/test_rev_list_parser.rb:21]:
<"object b2b1760347d797f3dc79360d487b9afa7baafd6a"> expected but was
<"[\"object b2b1760347d797f3dc79360d487b9afa7baafd6a\"]">.

Finished tests in 4.569215s, 45.9598 tests/s, 128.4685 assertions/s.                      
210 tests, 587 assertions, 3 failures, 0 errors, 0 skips

ruby -v: ruby 2.0.0p247-github6 (2013-06-27) [x86_64-darwin13.0.0]
rake aborted!
Command failed with status (3): [ruby -I"lib:lib:test:." -I"/opt/boxen/rbenv/versions/2.0.0-github6/lib/ruby/gems/2.0.0/gems/rake-10.1.1/lib" "/opt/boxen/rbenv/versions/2.0.0-github6/lib/ruby/gems/2.0.0/gems/rake-10.1.1/lib/rake/rake_test_loader.rb" "test/**/test_*.rb" ]

Tasks: TOP => default => test
(See full trace by running task with --trace)
```