Remove _add_defaults_data_files override

Fix spacing after comment hash.

Fix quantity of blank lines.

Fix spacing after comment hash.

Fix quantity of blank lines.

Sort manifest file list in tests

Different OS's and file systems return lists of files in different
orders, not always creation order. This caused intermittent test
failures.

The file list is now sorted prior to being checked to ensure a
consistent order across all systems.

Fixes #816

Fix issues with distribution location from eggs

Add 3.6-dev and nightly to travis configuration

Do not scan whole file tree when making MANIFEST

Just use backports.unittest_mock so that tox can be invoked naturally (without having to specify an env).