mat: modernisation

Modernises the MAT formula a little, especially around the handling of the Python elements.
Alright :'). Travelling right now but I'll fix this later tonight. Mike has collab rights over at my fork if he feels particularly generous ;).

Sent from my iPhone

> On 5 Nov 2014, at 16:40, Misty De Meo <notifications@github.com> wrote:
> 
> In Library/Formula/mat.rb:
> 
> > @@ -22,69 +22,78 @@ class Mat < Formula
> >    sha1 "932ac13863c994ca8874e3271f817efd879e28c3"
> >  
> >    depends_on :python
> mat's actually a Python library, not just a CLI application, so I think the :python dep was on purpose. It can't be installed via pypi.
> 
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