DOC/BLD: Prep README for version 0.2 release.

I will merge this just before I tag 0.2 If you are logged in, you should be able to read me draft of a release [here](https://github.com/soft-matter/trackpy/releases/untagged-4952b1a8a15012e5ef44). Comments welcome.

We should always test Travis on the DEPS that we recommend in the README, sans nose and perhaps pytables. The current recommendation in the docs is, I think, broken!

    $conda update conda
    $conda create -n test-broken numpy=1.7.1 scipy=0.13.0 matplotlib=1.3 pandas=0.13.0 numba=0.12.2 PIL pyyaml
    Fetching package metadata: ..
    Solving package specifications: ....
    Error: Unsatisfiable package specifications.
    Generating hint: .................................................
    Hint: numba 0.12.2* has a conflict with the remaining packages

The main issue is that numba 0.12.2 needs numpy 1.8. Scipy must be upgraded also. This is what my PR recommends:

    $conda create -n test-good numpy=1.8 scipy=0.14 matplotlib=1.3 pandas=0.13.0 PIL pyyaml numba=0.12.2
    Fetching package metadata: ..
    Solving package specifications: .
    Package plan for installation in environment /Users/danielallan/anaconda/envs/test-good:
    (...)

We'll see if Travis is satisfied.