updated athena lib (grid)
shells: cleaned up titles + descs.
Added ShellSelectorView.
Added ShellSelectorView to empty shell.
Shell Selector Styling.
player.html styling.
ShellSelector now swaps shells
Added DocView (markdown)

@ali01 @tenedor npm install
Remixer dropdown cleaner
RemixerView: show summary view.
shells: default description
Remixer: editable summary view.
Acorn title, description, thumb now shell-bound

The title, description, and thumbnail properties of acorn.Model
are now bound to their shell counterparts. This is because there
is no need for an acorn-level properties, since _all_ shells have
them (collections, wrappers, etc).
Video description quotes.
Editor header styling.
SummaryView rebind model events.