Filter sessions by available timeslots.
Merge branch 'develop'
Merged develop into master
Merge branch 'develop'
Patch session tags (fixes #176).
Merge branch 'develop'
Merge branch 'develop'

Conflicts:
	pyconde/schedule/admin.py
Merge branch 'develop'
Merge branch 'develop'
Merge branch 'develop'
Merged develop into master
Merged develop into master
Merged develop into master
Merge branch 'develop'
Merge branch 'master' of bitbucket.org:PySV/pycon_de_website
Fix slogan in header (fixes #185).
Omit seconds on session page (fixes #187).
Show language on session page and in schedule (fixes #190).
Merged develop into master
Add episode exporter as action.