Fix RsT in README (formatting/merge artifacts)

[stephendonner]

The raw RsT formatting is showing up on https://github.com/mozilla-services/axe-selenium-python/tree/02e6f352fea2067145a82c60d9b5bdbe890f98b4; looks like there are some merge artifacts which crept in, as well:

• https://github.com/mozilla-services/axe-selenium-python/blob/02e6f352fea2067145a82c60d9b5bdbe890f98b4/README.rst#L147
• https://github.com/mozilla-services/axe-selenium-python/blob/02e6f352fea2067145a82c60d9b5bdbe890f98b4/README.rst#L135
• more

[kimberlythegeek]

Not sure when, but this has been resolved