BLD: fix 2.7_LOCALE build
simplify install_travis.sh, always using a clean miniconda install
bump matplotlib to 1.4.0 for _LOCALE, numpy to 1.8.2

So this removes our testing of mpl 1.2.1 with numpy 1.7.1. We *still* test
elsewhere 1.7.1, and mpl 1.3.1 (with 1.8.2), so I think this is sufficient.

something changed in conda meta data to make the installtion of numpy=1.7.1 / mpl=1.2.1 fail
https://travis-ci.org/jreback/pandas/jobs/206680630

The only question is to we want to 'officially' say that we require mpl >= 1.3.1 ?
Things will still work as long as the installation succeeds, but travis is being problematic.

cc @jorisvandenbossche 
cc @tacaswell 