This patch removes some more dead code and documentation.
It also fixes a few typos I made when adjusting the transformation classes to pyHealpix.
Finally, there is a bunch of new regression tests for the issues Daniel and myself reported over the last weeks. Preliminary SHT tests for the GL grid are also included.
(The tests will be re-organized soon. However, I think it is good to have them in the master branch as soon as possible to prevent re-introduction of bugs.)