tools: Remove node.js pipbot implementation

We can now begin re-implementing in Python.

Issue #178.
build/tools: Add generic rule for Python scripts

Issue #178.
tools/pipbot: Begin re-implementation in Python

So far, we only have the version command working, but there's more to
come!

Issue #178.
tools/pipbot: Add 'help' command

Issue #178.
tools/pipbot: Add local file paths

Issue #178.
tools/pipbot: Refactor for better whitespace

Issue #178.
tools/pipbot: Add skeleton implementation of build()

Issue #178.
tools/pipbot: Load JSON configurations

Issue #178.
tools/pipbot: Implement build functionality

Issue #178.
tools/pipbot: Fail if command exits nonzero code

Issue #178.
tools/pipbot: Add 'deploy' command support

Issue #178.
tools/pipbot: Add 'wtf' command

Issue #178.
tools/pipbot: Update help text

Issue #178.
tools/pipbot: Add support to run commands quietly

If echo parameter is set to False, then don't print the command to be
executed.

Issue #178.
tools/pipbot: Add 'issue' command
tools/workflow: Don't use ghi to show issues

...this will be done by pipbot.

Issue #178.
tools/pipbot: Add 'new' command

Issue #178.
tools/pipbot: Add 'pause' command

Issue #178.
tools/pipbot: Add 'close' command

Issue #178.
tools/pipbot: Add 'release' command

Issue #178.