always bootstrap the current user if avail
split nav bar into partial
upgraded select2 to 3.4.5
[WIP] user impersonation

* basic functionality works
* needs permission checks (CanCan) and more testing
better feedback while impersonating
validate getting_started view
stop impersonating when value is cleared
better user filtering; extra option to stop impersonating
added some fancy icons to the user nav
fix login and logout
use font icon
initial permission/authorization implementation
added impersonate_users auth checks
useful can/cant helpers
added permission check
cleanup/refactor
implemented client-side permission checks