Merge pull request #49 from jhermann/ignore-buildpackage-files

Ignore paths in debian/ generated by package building
Remove commands that might run system's Python

These are dh_auto_build and dh_auto_clean, which don't make any sense
when we are running commands inside the virtual environment anyway.

Closes GH-51
Merge pull request #52 from nailor/avoid-system-python

Remove commands that might run system's Python
Update usage.rst

Documenting an "undocumented feature" ;)
Merge pull request #54 from schainker-digbil/patch-1

Update usage.rst
Merge remote-tracking branch 'origin/master'