added comment about parallelisation
fixed a nasty bug that would avoid computing type I errors. Very subtle. Subsets were not updated properly
added a unit test that checks whether bootstrapping statistics are the same for a custom kernel and a normal one
added a unit test for the custom kernel in order to check subset settings
added a comment on the previous bug that explains why one has to add/remove the indices every time
Merge pull request #897 from karlnapf/master

More unit tests and bugfixes for MMD kernel selection