reduce the number of git folds
make Git a higher level class, strategies Tarball, Clone, SshKey
split up git specs
fold the git tarball strategy
git ssh_key: keep msgs, use sh.newline for adding line padding, add specs
git tarball: rename oauth_token to auth_header, and simplify
Merge pull request #333 from travis-ci/sf-refactor-git

Refactor git