NEW: Add migration instructions between 0.4.x and 0.5.x.
NEW: Add migration instructions between 0.4.x and 0.5.x.

CondeNast/solr-node-client,godong9/solr-node-client,Bangsheng/solr-node-client,lbdremy/solr-node-client,nicolasembleton/solr-node-client,kfitzgerald/solr-node-client,lbdremy/solr-node-client,luketaverne/solr-node-client