Include LICENSE in the sdist.
Include LICENSE in the sdist.

The locustio sdist doesn't actually include the LICENSE:
```
$ curl https://files.pythonhosted.org/packages/e6/88/2d56405c715df8c4c94850857c581007d39fe50dfe9dbcac91e378a8f24f/locustio-0.9.0.tar.gz -L | tar tz | grep LICENSE
$
```

This fixes #788.

mbeacom/locust,locustio/locust,locustio/locust,mbeacom/locust,heyman/locust,locustio/locust,mbeacom/locust,mbeacom/locust,locustio/locust