Process rave metadata key for package metadata overrides.

This change allows the rave metadata prop to be an object or string,
opening up future expansion for extensions.  More immediately, though,
it lets the app metadata provide a rave object prop containing
overrides for package metadata.  Essential for bower packages that
don't yet specify moduleType. Keys in the overrides forcibly overwrite
existing keys.
Adjust code style to match existing
Adjust code style to match existing
Merge pull request #8 from RaveJS/add-metadata-overrides

Process rave metadata key for package metadata overrides.