Release 0.3.1 - outer elegance

Huge release with a ton of new features. Last release was in May!

• Allow other map options through extending google-map - commit - @jamstooks
• Fix the behavior of showCenterMarker attr with commit - @bamnet
• Added docs for google-search and google-directions - commit - @ebidel
• Allow map styling through styles attribute - commit - @ekryski
• Marker position correctly updates when its lat/lng change - commit - @ebidel
• Add zoomable attribute - commit - @bamnet
• draggable attribute can be used to disable panning - commit - @bamnet
• Maps sensor param is no longer required - commit - @brendankenny
• google-map-directions no longer requires a map - commit - @bamnet
• Info window are supported! Light dom content in google-map-marker. - commit - @bamnet