Add support for Travis and Coveralls in a future-compatible way

This pull request is an alternative to yhat/ggplot#45. The main differences are that we fully embrace `setuptools` and `pip`, which are what most people use for package management these days, instead of trying to get by with `distutils`. According to [PEP 453](http://www.python.org/dev/peps/pep-0453/), `pip` will be included with Python starting on November 20th, and all official documentation (even for Python 2.7) will be updated to recommend using that instead of `distutils`.

Like yhat/ggplot#45, this PR also adds support for using Travis and Coveralls for automatic unit testing and coverage information. We greatly simplify the Travis installation by using `conda` to install the latest binary versions of all requirements.

As a bonus, I also removed `README.md` (because GitHub will just render `README.rst` without it) and updated `README.rst` to have all the same information (and images) as the previous version of `README.md`.