Support auto-update

[LeoColman]

Add an update every 30s to the current screen, so that we can have real time data

[LeoColman]

@iamtoruk I think this new feature broke optimize; I can't read it because when it auto-updates I go back to "Today"

[iamtoruk]

Good catch, thanks. Fixed in #109. Auto-refresh no longer resets the optimize view, and period switching (arrow keys + number keys) now works in optimize and compare without kicking you back to the dashboard. Update to 0.8.1: npm install -g codeburn@latest