Fix Workspace Chevron in FF

Summary:
* changed pseudo element from :after to :before
	* any element that has float right has to come first in FF

Test Plan: test workspace in FF

Reviewers: rjmackay

Reviewed By: rjmackay

Subscribers: shadowhand

Maniphest Tasks: T151

Differential Revision: https://phabricator.ushahidi.com/D80