[#708] Fix render_markdown() helper function
[#708] Switch over to use markdown_extract() not misc.py
[#708] Fix tests
[#708] Get markdown_extract() to use RE_MD_HTML_TAGS
[#708] Minor refactor
[#708] Clean up code, fix comment, remove obvious comment
[#708] Add more tests to link detection tests
Merge remote-tracking branch 'okfn/master' into 708-markdown-fixes

Conflicts:
	ckan/controllers/user.py
Merge pull request #708 from okfn/708-markdown-fixes

Markdown fixes