Add cairocffi to requirements
Merge branch 'beta' into remove_rsvg

Conflicts:
	requirements.txt
Add django csrf token to jquery ajax calls
Add file download feature back in, w/ cairosvg.
Remove editor backup files that should never have been committed in the
first place anyway
Get rid of unused function
Make download URL absoluter
Check svg data for validity.
Fix wrong form field name
Fix strange bug where file name was changing after first download.
Spaces in content-disposition header filename causes firefox to ignore
everything after the space, so replace with underscores