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 
merging to avoid constant travis failures, but please comment on the question I raised above. I have no problem with bumping the minimal matplotlib version from 1.2 to > 1.3.1 (1.3 dates from 2013 I think, so we might even go to 1.4? cc @TomAugspurger @sinhrks ). 

Should probably open a separate issue for that to remind of code clean-up and update of docs. Ah, I see that in practice > 1.3.1 actually means >= 1.4 (1.4.0 dates from August 2014). But as I said, that sounds good to me to bump to that.