Patch build

Due to a problem with 0.2.3 pip builds that was affecting at least one user, I released v0.2.4 as v0.2.3 + commit aea9fcc below. It removes ez_setup, which was more trouble than it was worth. I built conda packages for PIMS and trackpy on all five platforms. They are on a [soft-matter binstar channel](https://binstar.org/soft-matter). To install trackpy on any platform, users need only type:

    conda install -c soft-matter trackpy

So, this PR:
* brings the v0.2.4 patch into `master`
* updates the README to recommend a conda build

By all means open another PR to refine the README edits, but I'm going to merge this now to get this out there.