Add on offline Exception.
Merge branch 'offline' of github.com:toomore/grs into class-except
Raise class.
Add error.py
Rename.
Update version.
Add error docs page.
Add `ConnectionError` into realtime.
Fixed urllib2 str format.
Fixed str format style.
Merge branches 'realtime' and 'class-except' of github.com:toomore/grs into v0.5.3rc

Conflicts:
	grs/realtime.py
Update docs.
Add error link into docs index.
Merge branch 'v0.5.3rc' of github.com:toomore/grs