Add erlang R16B1

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Package elixir and rebar.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Add meta for elixir & rebar.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Add myself as a maintainer to erlang R16B1 and elixir.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
generated python packages for Plone and Pyramid
removing existing plone packages
pypi2nix packaged, Distutils2 added to generated python packages
json wasnt formatted correctly and updating pypi2nix script
updated beautifulsoup4 and waitress
add python application substanced and it's dependencies
Merge pull request #815 from garbas/pypi2nix

pypi2nix - generating packages from pypi
typo
python: fix alot by having magic and python_magic packages
python-magic: git -> 0.4.3
thunderbird: reenabling parallel building

It built fine here. Maybe the previous failure was of a particular version.
Updating vim and vim_configurable to 7.4.

I change vim_configurable from 'latest' to 'default', as 'default' now is more
recent than latest.
Marc Weber suggests to drop 'latest' in vim_configurable.
libav: major update and refactoring

Also leaving 0_8 branch, as it's compatible with older ffmpeg versions.
I'm planning that all expressions will be able to switch easily
between ffmpeg and libav (whatever default we choose, but I prefer libav).
Update leiningen to 2.3.1.
fix nixpkgs eval