BLD: use wheel packages to reduce travis-ci build times.
Roughly from 40 minutes to 13 minutes.
Before: https://travis-ci.org/pydata/pandas/builds/8738816
After: https://travis-ci.org/y-p/pandas/builds/8749214

The existing build cache system for 2to3 and cythonized caching can knock this
down much more, but it's more fragile and part of the reason the previous attempt
ultimately failed. Really need to do that in a jenkins server somewhere , if at all.

There's no opt-in/whitelist  anymore. faster for everyone.
The building of the dependencies (a rare occurence) is automated in a provisioning
script for vagrant under ci/speedpack. should just be 'vagrant up' and step away for an hour.

The package files are hosted on a private openshift server but if a bus hits me it's all here for
someone to plunk down a static file webserver somewhere and tweak the url.

In case this goes bad and I'm not around to notice, there's one line to comment in
ci/install.sh. cc @jreback @cpcloud

enjoy.
