check existing via a map instead of a lodash.find
only do map check if theres a single primary key
lets not break tests already
get rid of _.omit
fix test
don't set previous value in loop if raw
upgrade to dottie 0.2.1 which has .transform performance improvements
don't attempt to check for or convert dates if raw, date conversion from the db is currently handled in the drivers
Merge pull request #1555 from sequelize/perf

Performance improvements on includes