Add tests for RST rendering

```
❯ py.test -v
============================================================================= test session starts ==============================================================================
platform darwin -- Python 2.7.6 -- py-1.4.26 -- pytest-2.6.4 -- /Users/marca/python/virtualenvs/readme/bin/python
collected 8 items

tests/test_rst.py::test_rst_001 PASSED
tests/test_rst.py::test_rst_002 PASSED
tests/test_rst.py::test_rst_003 PASSED
tests/test_rst.py::test_rst_004 PASSED
tests/test_rst.py::test_rst_005 PASSED
tests/test_rst.py::test_rst_006 PASSED
tests/test_rst.py::test_rst_007 PASSED
tests/test_rst.py::test_rst_008 PASSED

=========================================================================== 8 passed in 0.48 seconds ===========================================================================
```