[PyFeyn] My changes committed

[George S. Williams]

Hello, Georg and Andy,

I committed the few changes that I have

 From the ChangeLog-
2014-03-31 George S. Williams <pysiscist at websterling.com>

     * Changed subprocess.check_output to subprocess.Popen in call to
     kpsewhich to allow it to work with Python 2.6

     * Added the CrossMark class contributed by Jeremi Piotrowski
     (<jeremi.piotrowski at gmail.com>)

     * Modified draw in Class FeynmanDiagram to allow adding padding
     around generated image

The only other suggestions I have at this time-
Include the examples directory when the next update is packaged- it has 
been missing since 0.3.3

The hepnicenames PDF might be a useful addition to the package

Hope that you find this useful,
George