fix non-existent collaborator error
Catch / in collaborators' names
Merge pull request #306 from migeruhito/collaborators

Crash when a non-existent collaborator is added to a worksheet
Add gettext back in files descended from twist.py
Merge branch 'master' into gettextbackin

Conflicts:
	sagenb/flask_version/worksheet.py
Add a few more missed translatable messages
Merge pull request #308 from kcrisman/gettextbackin

Add gettext back in files descended from twist.py
spanish translation updated
More updates to spanish translation