added in two new references from PLOS, close #114
added in two new references from PLOS, close #114

jhollist/10-simple-rules-data-storage,fmichonneau/10-simple-rules-data-storage,emhart/10-simple-rules-data-storage,naupaka/10-simple-rules-data-storage,snim2/10-simple-rules-data-storage,karawoo/10-simple-rules-data-storage,PBarmby/10-simple-rules-data-storage