Initial revision of sticky headers, flickers a bit on scroll
Updated sticky headers to use position:fixed

Left in the former "transform" method as an option. The transform
option requires only style updates instead of a bunch of DOM
manipulation, but flickers, whereas fixed doesn't.
Reverting CSS changes, the header is now cloned within its original parent
Fixing a typo
Tweaked injection logic
Removed css transform dependency from sticky headers
Added nested sticky headers support
Added gradual scrollaway for sticky headers
Adding more documentation and cleaning up unused code
Fixed a sticky header bug where offsets were being added for non-nested parents
Added support for resizing sticky headers on window resize
Integrated sticky headers in the style guide
Updated the styleguide documentation for sticky headers
Added support for same-depth sticky headers (as long as they're from a different selector part)

This is used for the new event logs, also added .advanced-filters to
defaults.
Merge remote-tracking branch 'origin/develop' into feature/fixed_widget_headers
Added partially working footers to sticky headers
Fixed an issue with same depth different selector items were stacking improperly
Fixed a bug where the "stickyable" state of items wasn't being cleaned up correctly, resulting in improper stacking and orphans
Fixed a bug when toggling tree items where ".tree-open" was being removed incorrectly

Also updated the sticky header style guide to more accurately represent
true application state (all items are pre-opened via click instead of
hard-coding).
Fixed some styling issues and sticky items not repositioning on window resize properly