Some small changes

Someone reminded me of easing curves again today for the first time in ages, and then I remembered that there were a few loose ends in this that I wanted to clean up and never did, so here we go.

Changes:

• Documentation
• Changed easing_get to ease, mainly because ease has the same number of characters as lerp
• ease can now also take a string name as the curve type, if you prefer doing that for some reason - see the documentation for the curve names