more nested less rules - navs component

* Convert more inline advices (compatibility, dependencies, ...) to
sidenotes
* Add sidenotes for:
** Note on plugin dependencies in general
** Required padding for navbar-fixed- (incl. code snippet)
* Fixed text for the small tag

IE8 doesn't need help with responsive images, they work just dandy apparently (see http://jsbin.com/idesit/1)

* I propose: make the docs rely more heavily on the new design language,
replace alerts (not the .alert examples) by sidenotes.
* Remove alert-heading class, which no longer exists in CSS.

Remove BOOTSTRAP_RESPONSIVE_LESS in css compile

fixed typo in typography documentation

Fix docs.html Table Row Danger CSS Class

No more needed in Bootstrap 3

[3.0.0-wip] Reordering variables that were being used before they were declared. Fixes compiler crashes.