add arpack-3.1.4
Don't set shells as default whenever enabled

Because alternative shells like Zsh are almost non-functional unless
"enabled", it doesn't make sense to try setting them as default just
because they are enabled.
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 vobsub2srt-git-20131228-1c782e5
keepassx: add version 2.0alpha5