Add http options and connection-manager

Adds the connection--manager function to return a connection manager.
Adds an option map to each api function that is used in constructing the
http request.  The return value of connection-manager can be passed in
the options on the :connection-manager key to enable persistent
connections.
Add back api compatability

Also adds logging for deprecation warning.
Merge pull request #1 from hugoduncan/feature/add-persistent-connection

Add http options and connection-manager