allow for trapping postgres connection errors

connect() returns an event emitter which can be used to handle errors
gracefully rather than throwing an error in callback which would
terminate the entire node process
fix #334 ('include' places a "null" element to the result if no data is related)
reuse existing DAO.identifiers
Added ENUM type
Fixed a typo in PG Query Generator ENUM update
Added DataTypes require to PG and SQLite Query Generator
Fixed a typo in PG Query Generator
Added a few tests, DRY'd out some PG ENUM code
fixes #204 thanks to @bpartridge
use native array method
increment and decrement added
update changelog
enable single field instead of array
comment back tests
postgres and sqlite increment
sqlite and postgres works and fix test for postgres
tests are back
adapt decrement tests to postgres as well
fix unrelated jasmine/sequelize tes
Travis bump