update readme to reflect latest changes to APIs
update readme to reflect latest changes to APIs

romainr/spark-solr,wmudge/spark-solr,epheatt/spark-solr,rahulsharma1991/spark-solr,LucidWorks/spark-solr,XiaoqingWang/spark-solr,matthoffman/spark-solr,shirney/spark-solr,Stratio/spark-solr,yonglehou/spark-solr