First pass at help screen.
Fixes problem presenting help VC from within a modal.
Adjusted help button metrics.
Merge remote-tracking branch 'artsy/master' into help

Conflicts:
	Kiosk/App/AppDelegate.swift
	Kiosk/Storyboards/Auction.storyboard
	docs/CHANGELOG.md
Merge pull request #118 from AshFurrow/help

@1aurabrown => Help screen