First attempt at HTML dependency management
Fix initial dependency handling, fix knit_print
Remove unused class
Use html_dependencies for showcase mode

For some reason, showcase mode was breaking sliders without this (e.g. 06_tabsets)
Use html_dependency for date inputs, datatables
Fix bootstrap themes
Include html-preserving comments in knit_print
Ensure dep.meta is an array
Merge branch 'html-deps'

Code reviewed by @jmcphers

Conflicts:
	DESCRIPTION
	R/bootstrap.R
	R/reactives.R