Adds git-remote-hg as submodule in the vendor directory.
Adds git-flow-completion as submodule in the vendor directory.
Adds script to bashrc.d to easily include vendor scripts
Deletes symfony2 autocomplete script as this is now added as submodule.
Makes include-vendor-scripts more robust

 - Improves the code that tries to find the original directory the sourced script is in.
Adds heroku bash completion as submodule in vendor directory.