adjust height of extended fixed nav

[lsrock1]

problem: when i want to use fixed navbar with Extended Navbar with Tabs,
tab contents are covered by tab buttons because .navbar-fixed's height is just set to $navbar-height or $navbar-height-mobile without tab's height. (content's div tag goes up to bottom of navbar)

code: http://codepen.io/anon/pen/egBqZR

So i make new class, navbar-extended-fixed. Its height is set $ navbar-height + $tabs-height to widen the height and cover all the tab area.
In variables.scss file i add new variable, $tabs-height to reflect tab's change automatically because tabs-height is accessed in navbar and there is a possibility that some tab's changes in the future breaks nav'css
This tag can be used exactly same way like navbar-fixed.

after code: http://codepen.io/anon/pen/mRONQy

[lsrock1]

One more thing, With fixed-nav sidenav doesn't work. sidenav-overlay covers everything. After i change the z-index of fixed-nav 997 to 998, it works.
Thanks for your works!