Add license text to LICENSE
Components class: remove unnecessary private method

Just use the `get_active()` method, and remove the unneeded
`_reset_active()` method.
Unit tests: prepare to update the uninstall testing tools

We’ll now be simulating plugin usage during the uninstallation tests as
we did before. See #16.
Squashed 'tests/phpunit/includes/uninstall/' changes from ae183d4..427d1c5

427d1c5 Allow for simulation of plugin usage before uninstallation
0f452f6 README: first pass at adding some usage info

git-subtree-dir: tests/phpunit/includes/uninstall
git-subtree-split: 427d1c560012733dfaed1258865ba49aa718cbe9
Merge commit '940a031a1c40b9648151fb87030ba243bb35b62c'

Now we simulate plugin usage during the uninstallation tests.

See #16