Fixed errors on geoNear and geoSearch
Fixed errors on geoNear and geoSearch

Previously, these commands would return the raw db command object, not
checking for errors or anything. This now checks to see if the command
succeeded, and if it did not, creates and returns an appropriate error
message.

segmentio/node-mongodb-native,BlueRival/node-tokumx-native,mongodb/node-mongodb-native,flyingfisher/node-mongodb-native,elijah513/node-mongodb-native,BlueRival/node-tokumx-native,PeterWangPo/node-mongodb-native,mvnnn/node-mongodb-native,amit777/node-mongodb-native,capaj/node-mongodb-native,agclever/node-mongodb-native,d-mon-/node-mongodb-native,christophehurpeau/node-mongodb-native,patriksimek/node-mongodb-native,rafkhan/node-mongodb-native,thenaughtychild/node-mongodb-native,janaipakos/node-mongodb-native,HiLittleCat/node-mongodb-native,tuyndv/node-mongodb-native,mongodb/node-mongodb-native,sarathms/node-mongodb-native,jqk6/node-mongodb-native,Samicelus/node-mongodb-native,Lapixx/node-mongodb-native,hgGeorg/node-mongodb-native,mongodb/node-mongodb-native,zhangyaoxing/node-mongodb-native,nahidcse05/node-mongodb-native,HBOCodeLabs/node-mongodb-native,mongodb/node-mongodb-native,pakokrew/node-mongodb-native,dnanexus/node-mongodb-native,beni55/node-mongodb-native