Added responsive classes to nav-collapse div

Added classes 'collapse' and 'navbar-responsive-collapse' to the nav-collapse div on line 44.  Dropdown menus were not responding properly in the collapsed response state.  Adding these two classes fixed this for me.
Merge branch 'master' of github.com:iepathos/pinax-theme-bootstrap into iepathos-master

Conflicts:
	pinax_theme_bootstrap/templates/theme_bootstrap/base.html
Merge branch 'iepathos-master'