Add Cython to TravisCI file
Add Cython to TravisCI file

This should fix the Travis error:
```
Collecting pyutmp (from -r .travis.requirements.txt (line 16))
  Using cached pyutmp-0.2.1.zip
    sh: 1: cython: not found
    Failed to build "pyutmp_linux.c" from "pyutmp_linux.pyx"
    "pyutmp_linux.pyx" is newer than "pyutmp_linux.c". Rebuilding "pyutmp_linux.c".
    + cython pyutmp_linux.pyx
    Complete output from command python setup.py egg_info:
    sh: 1: cython: not found

    Failed to build "pyutmp_linux.c" from "pyutmp_linux.pyx"

    "pyutmp_linux.pyx" is newer than "pyutmp_linux.c". Rebuilding "pyutmp_linux.c".

    + cython pyutmp_linux.pyx

    ----------------------------------------
    Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-b6Ahv_/pyutmp
```

MichaelDoyle/Diamond,MichaelDoyle/Diamond,gg7/diamond,skbkontur/Diamond,skbkontur/Diamond,gg7/diamond,python-diamond/Diamond,gg7/diamond,tusharmakkar08/Diamond,MichaelDoyle/Diamond,MichaelDoyle/Diamond,skbkontur/Diamond,python-diamond/Diamond,gg7/diamond,tusharmakkar08/Diamond,tusharmakkar08/Diamond,skbkontur/Diamond,tusharmakkar08/Diamond,python-diamond/Diamond