Fix unable to detect schema conflict (#208)
Fix unable to detect schema conflict (#208)

This only happens when saving multiple records with a
schema-incompatible record being latter than schema-compatible ones.

refs #140
rickmak/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,SkygearIO/skygear-server,SkygearIO/skygear-server