services: Add YourlsService for Yourls-based URL shorteners
services: Add Vbly (http://vbly.us)
services: Add Arsehat (http://arseh.at)
Adds Visibli/SharedBy.
services.py: Uses a dict instead of long if case.
Merge pull request #8
services.BaseVisibliService: Use unexpected_http_status mechanism to handle iframes
Merge branch 'yourls'

Conflicts:
	tinyback/services.py
Bump verison number to 2.8