Polish

Minor cleanup:

• Progress bar styling
• Cleaned up docs
• Small tweaks to existing apps (RSS Reader, Announce)

Feature changes:

• Paranoia filtering of all inputted values - even from reasonably trustworthy sources
• Global flag to set if you prefer Celsius for everything
• Add battery status to all possible devices
• Simple Chromecast device (see if it's on and pass in a YouTube ID - that's it)
• Air Quality device + app to alert if things get bad
• Twitter app allowing you to Tweet at your house to have it read aloud or delegate to Gerty to issue commands.