TNL-1891 Browse Teams: Category Subnavigation

Introduces a tabbed view component which displays its subviews and
handles Backbone navigation between each tab. This is used to implement
the "My Teams" and "Browse" areas of the Teams tab. Right now the
content of both tabs is stubbed out with a placeholder view which should
be replaced by TNL-1893 and TNL-1892.

common/test/acceptance/pages/lms/teams.py

@@ -18,4 +18,4 @@ class TeamsPage(CoursePage):
 
     def get_body_text(self):
         """ Returns the current dummy text. This will be changed once there is more content on the page. """
-        return self.q(css='.teams-text').text[0]
+        return self.q(css='.page-content-main').text[0]