tools/pipbot: Fix usage check in release command

Pipbot will now give you usage instructions if you don't give a valid
command.

Issue #178.
tools/pibpot: Remove unused variable

Issue #178.
tools/pipbot: Rename 'new' command to 'start'

Issue #185.
tools/pipbot: Move usage check into start()

Issue #185.
tools/pipbot: Add dummy start() implementation

This accepts and differentiates between version, issue number, and
release version commands by regexp matching.

Issue #185.
tools/pipbot: implement start_new_release()

Issue #185.
tools/pipbot: Import PythonGit

Issue #185.
configure: Check if python is installed

... only if we are building tools.
configure: Check for python git module
tools/pipbot: Implement start_new_feature()

Issue #185.
tools/pipbot: Implement pause()

Issue #185.
tools/pipbot: Implement finish

Issue #185.
tools/pipbot: Update help text

Issue #185.
tools/pipbot: Remove unneeded 'release' command

This has been supplanted by the new start|pause|finish commands.

Issue #185.
tools/pipbot: Match prefixes in branch names

Issue #185.
Merge branch 'feature/185'
tools/pipbot: Fix branch name deletion

Issue #185.