Unpacking from git source cache: Use 'git clone' instead of 'git archive'
Support for git submodules in source cache
Attempt to change travis.yml to VERBOSE=1 during testing
Merge remote-tracking branch 'origin/master' into HEAD
Improve Git submodule support

* Allow patches to be unpacked into git clones (now fetches)
* Use temporary branches to fetch specific commits
* Support relative paths with submodules
Generalize Git submodule testing

* Use CWD instead of GIT_DIR in test Git commands because in certain
  versions of Git submodule commands will fail when GIT_DIR is set.
* Fix os.listdir() order assumption
Merge pull request #214 from hashdist/git-submodules

git init/fetch instead of git archive + git submodule support