Revert to performing `push` before `release` so that any upstream conflicts will prevent a release.
TagCommand by default (but optionally) invokes `git push origin` in addition to `git push --tags origin`.

Pushing commits in addition to tags seems to be the least surprising course. However, there are times when commits have already been pushed (e.g. from BumpCommand), so it is necessary to make this an option to avoid doing it twice.
Bump to 0.5.3