Fixes to sign-in form; changes to helpers; specs
	- Set up a functional Bootstrap drop-down sign-in form,
		with less verbose styling
	- Fixed JS so that and all other Bootstrap drop-downs
		don't close when you click in them
	- Replaced full_title helper with page_title helper, which
		generates both h1 and title tags
	- Wrote specs for page_title and show_errors helpers
	- Added options param to gravatar_for in users_helper.rb
Rspec tests should be randomized