Provide second person forms assert_raise, assert_throw and assert_include

This PR provides `assert_raise`, `assert_throw` and `{assert|refute}_include` while aliasing existing `assert_raises`, etc.

This:
* provides consistent api with other minitest assertions like `assert_send`, `assert_respond_to`, `assert_output`, `assert_match` and `assert_equal` and thus reduces cognitive load.
* makes api consistent with Ruby's established naming convention, see for example http://stackoverflow.com/questions/5280556/why-does-ruby-use-respond-to-instead-of-responds-to

Thanks