filezilla: use default gnutls instead of vulnerable gnutls2
add vobsub2srt-git-20131228-1c782e5
zsh: don't clobber the environment of non-login shells
Add biber-1.8 and dependencies
add mathematica-9.0.1
Build numpy against openblas
Don't set a default version of Mathematica

Nixpkgs should not set a default version of Mathematica. Many users of
Mathematica have institutional licenses and do not have immediate access
to new versions. If there is a default version in Nixpkgs, updating that
version will cause trouble for all such users.
Add pcmanfm-1.2.0