Allow using alternate api-root for post and get

YambaClient library has built-in default api-root:
 "http://yamba.marakana.com/api"
But the training services of marakana appears to have been taken
over by newcircle, so we do small refactorings to be able to
specify an alternate api-root
 "http://yamba.newcircle.com/api"