Extra things for the Travis build

I've added a few things:
 * Run tests with coverage
 * Send coverage to Coveralls
  * It gives a report like https://coveralls.io/r/hugovk/twarc
  * Test coverage is 62%
 * Add more Python versions to build
  * All Py2 pass
  * Py3 fail, but are marked as allowed failure for visibility and fail block the build
    * I fixed some Py3 print/import problems
    * There's still a remaining str/bytes issue
 * Update .gitignore
 * Show static analysis at end of build
 * Fixed some static analysis things