[bugfix] add sorting to mongodbs find
[bugfix] add sorting to mongodbs find

When migrating down, the migrations doesnt get ordered right. This is because of the
missing sorting of found result sets from mongo db.

Fixes #242

snordrapidimages/node-db-migrate,vertiman/node-db-migrate,ViGo5190/node-db-migrate,apechimp/node-db-migrate,bwiggs/node-db-migrate,andela-ooladayo/node-db-migrate,cqricky/node-db-migrate,SamuelBolduc/node-db-migrate,db-migrate/node-db-migrate,db-migrate/node-db-migrate,chatter/node-db-migrate,jrdi/node-db-migrate,ror/node-db-migrate,MForMarlon/node-db-migrate,marbemac/node-db-migrate,ramakrishnan/node-db-migrate