python: New style
Improved audit of python stuff
keg.rb: minor comment fix
yle-dl: depends_on :python
terminal-notifer: Removed caveat.

Without code signing, it *does* work. All is happiness.
hg-flow: 0.4

* depends_on :python
* Install hgflow.py into `python.site_packages`
* Use default branch for --HEAD
* Work around naming bug for 0.4 download
* Update caveats (`hgflow=` is enough)
python: simplify how PythonInstalled is used in python.rb

* Should also be more robust as we now explicitly set the
  python.binary.
python3: Added HEAD and distrubute 0.6.45

* Use `build.with?` instead of `build.include? 'with…'`
* Reuse PythonInstalled.new.modify_build_environment
* Use `test do` instead of `def test`
terminal-notifier: Remove outdated comment.
python_helper.rb: Little comment improvement
Python: Don't print warning about PYTHONPATH

Authors should use `python.standard_caveats` instead.

* Accessor for python.binary
* Made `python.brewed?` more robust if no python found at all
* python.brewed? is more relaxed now and allows older versions
  of the Python formula.
* Only print about wrining sitecustomize.py and distutils.cfg if
verbose and debug.
youtube-dl: Python 2.x and 3.x support
python3: Fix build with brewed-tk & don't link X11
python: Fix --with-brewed-tk