[FEATURE] Add before_install git submodule update (http://about.travis-ci.org/docs/user/build-configuration/#Updating-Git-Submodules)
[BUGFIX] Use public Git URL for GIT submodule (http://about.travis-ci.org/docs/user/build-configuration/#Use-Public-URLs-For-Submodules).
Merge pull request #4 from braingourmets/travis-submodule