Remove non-leap_doc sources.

When #5300 (closed) is resolved we need to remove all the other docs sites.

http://bitmask.readthedocs.org/en/latest/ http://bitmask.rtfd.org/ (may be a shortcut for the previous one) http://pythonhosted.org/leap.bitmask/

any other?

(from redmine: created on 2014-03-14, closed on 2014-03-31, relates #5300 (closed), relates #4239 (closed))