Problem with collapsed menu bar when page is 980px wide

Created by: bhopwood

There is a problem with the operation of the collapsed menu bar when the page width is exactly 980px wide. Clicking on the 'btn-navbar' will expand the menu but clicking again causes the menu to close then open immediately.

This seems to be caused by a problem in 'responsive.less' where there are conflicting definitions for 'max-width: 980px;' and 'min-width: 980px'

I have tested a solution by changing the 'max-width' to 979px, so that <980px uses the collapsed menu and >=980px uses the normal menu bar.

Before I submit a pull request the question is - is the policy that 980px wide displays use the collapsed menu form or the standard form?