Exclude relative href links from http check
Refactor linkcheck logic in doc_generator

Forum URLs, e.g. http://www.openmicroscopy.org/community/viewforum.php?f=11
were not properly parsed by the current implementation. Replaced the
linkchecking logic using the one from SPhinx linkcheck.
Fix indentation
Fix url variable name
Remove optional argument from Request
Fix broken links condition
Merge pull request #18 from sbesson/doc_generator_fix

Doc generator fix