Move Routing section and add to README ToC
Move Routing section and add to README ToC

Promote the Routing section of the README to an H3, move it out of (what looks like) the middle of the Serializer section, and add it to the ToC.
AKHarris/jsonapi-resources,togglepro/jsonapi-resources,localytics/jsonapi-resources,kevintraver/jsonapi-resources,senid231/jsonapi-resources,harisadam/jsonapi-resources,jsmestad/jsonapi-resources,cerebris/jsonapi-resources