Add travis build matrix with include so that tox only tries to run tests in python 2.7 in travis's python 2.7 virtualenv and only tries to run tests in python 3.6 in travis's python 3.6 virtualenv.
Add travis build matrix with include so that tox only tries to run tests in python 2.7 in travis's python 2.7 virtualenv and only tries to run tests in python 3.6 in travis's python 3.6 virtualenv.

tdpreece/ApprovalTests.Python,approvals/ApprovalTests.Python,approvals/ApprovalTests.Python,approvals/ApprovalTests.Python