Fix return value of git.checkout

The rest of the function returns either True or False.
git would return an error code 0 in this case, which corresponds to True here.
Merge pull request #122 from po1/patch-2

Fix return value of git.checkout
Fixing bug in travis builds

Trying to get travis rolling again.

Trying to debug travis

Potential fix for travis

force push tags from GitClone

Only force push tags on failure of normal tags

fixup pep8
Better handling of missing url in rosdistro for bloom-release
Added automated pull requests
Polishing of the automated pull request mechanism
If the package name == path, use None in rosdistro
Merge pull request #125 from ros-infrastructure/issue_125

bloom-release should ask the user for the release repository url if it is not in the rosdistro file
Merge pull request #126 from ros-infrastructure/autopr

Automated pull requests
Updating CHANGELOG.rst for 0.3.3
0.3.3
updating upload url
adding raring
Ensure valid current version before warning
Merge pull request #129 from ros-infrastructure/issue_129

old version detector gives false positive on first run after update
Added global arguments to bloom-release
Added an info msg to the transactional git commit
Improved message upon pull request failure

Also fixed a typo in the generation of repository
entries in the rosdistro file.
Making the required versions of deps consistent
Merge pull request #130 from ros-infrastructure/issue_130

Debian package python-bloom should specify the correct version of dependencies