Refactor tox.ini and update README.

This commit contains a few usability fixes:
  * Expands the default README.rst by adding a small examples section.
  * Refactors tox.ini to reduce boilerplate and expand test coverage.
  * Fixes all checkstyle and import sort violations so that those can
    now be run as part of the default tox test suite.
Fix minor typo in README.rst.
Merge master.
Add more to coverage integration test.
Fix integration coverage.
Set executable bit for coverage.sh