allow pip to install Mac wheels from pypi (in addition to Windows wheels)
Simplify the script that we install

* Solves an issue where distlib decided it was a sane thing to do
  to swallow stack traces by default
* Simplifies the script drastically
* Adds a note about why we need to set the variants
Remove concurrent test runs because they are failing randomly
Merge pull request #1286 from dstufft/fix-distlib-script-defaults

Simplify the script that we install
Merge pull request #1295 from dstufft/serially-run-tests

Remove concurrent test runs because they are failing randomly
Merge pull request #1278 from qwcode/allow_mac_wheels

allow pip to install mac wheels from pypi
`pip.locations.distutils_scheme` should read distutils config files
Merge pull request #1297 from qwcode/parse_distutils_config

`pip.locations.distutils_scheme` should read distutils config files
better message for the failure log