Bounce the arrows when a dashboard value changes

Closes #414
Merge pull request #416 from quintel/delta-bounce

Bounce the arrows when a dashboard value changes
Adjust hurdle values for household appliances

The last appliances (the TV in the bedroom) will now appear when the
appliances slider is set to 90%, instead of 40%.

Closes #367.
Add better site description to the "tweet" button

Ref #348
Add meta tags to produce better Google+ shares

Ref #348
Put the social media image on S3
Add meta-tag names
Final tweaks for Google+