Added superop_reps to apidoc.
Added new section to guide on superops, superop_reps.
Merge remote-tracking branch 'upstream/master' into doc-superrep
Added more details, biblio, ignored *.pyx.
Fixed problem with bibliography format, added extlinks.
Merge pull request #6 from cgranade/doc-superrep

Started documentation of new superoperator and superrep functionality.