Abstract validation into a separate class method
Fix aggregate and composite queries: https://github.com/balderdashy/waterline/commit/df9cbfb057a6c8dc5b42ffdbfb119deb0d06226c#diff-eb5f3fb865a72bdd11ebf4249d965f06
Add model instance validate() method and unit test
Merge pull request #144 from ragulka/abstract-validation

Abstract validate() method