added option allowAccountsMerging
added option allowAccountsMerging

lucaslizama/core,gwendall/core,fpoirier1/core,niole/core,lucaslizama/core,abernix/meteor-useraccounts-core,gevou/core,jjeffwarner/core,niole/core,jxm262/core,phocks/core,rawGem/aus-core,meteor-useraccounts/core,jonxduo/core,dandv/core,ShawnOceanHu/core,gevou/core,challett/core,meteor-useraccounts/core,jjeffwarner/core,phocks/core,logankoester/core,evgenTraytyak/core,logankoester/core,rawGem/ua-core,evgenTraytyak/core,PhilippSpo/core