Travis-CI Test Running and Coveralls Coverage Reporting

You can now see reports on urbansim's test runs at https://travis-ci.org/synthicity/urbansim and reports on how much of the code is covered by the tests at https://coveralls.io/r/synthicity/urbansim. The results are also displayed in the README as badges small badges:

![screen shot 2014-03-14 at 1 37 29 pm](https://f.cloud.github.com/assets/920492/2425637/828b02ba-abb8-11e3-9cfa-b288a42a923e.png)

(I think the coverage badge will update once this is merged to master.)