WIP: options for runner plugins
Add interface class for runner plugins
Eliminate need for extra DriverManager by reducing indirection to get
extension that is already loaded
Rename methods to reflect correct tests
Fix a test
Fix some tests
Fix tests
Reduce duplication
Fix Python 2 compatibility
Fix coverage complaint on abstract method
Add docstring
Add tests
Don't cover some multiplatform code
Merge pull request #81 from sjagoe/runner-plugin-opts

Runner plugin opts