Potential fix for #1057

Tests for the undo flag would definitely be a good idea, too.
Merge branch 'issue_1057' of https://github.com/elliotf/sequelize into elliotf-issue_1057

Conflicts:
	bin/sequelize
run undo tests for the flags "--undo" and "-u" as well
sequelize --undo
better check if 'IS NOT' or '!=' should be used
added tests for postgres and sqlite
set the right context for postgres tests
Merge pull request #1231 from unlooped/master

better check if 'IS NOT' or '!=' should be used
Update changelog.md
Update README.md
Validation skipping logic was inverted. Fixed #1169
Merge pull request #1233 from saschagehlich/bugfix/inverted-validation-skip-logic

Validation skipping logic was inverted. Fixed #1169
Update changelog.md
Sequelize.ENUM can now take values as arguments or as a single array argument
Fix test to use `field: Sequelize.ENUM` when passing values directly to the type
Fix for #1234 - Postgres query should set on .dataValues instead of object directly
Update changelog.md
Moved normalizing of attribute.values to DaoFactory#define
Merge pull request #1239 from mickhansen/fix-issue-1234

Fix for #1234 - Postgres query should set on .dataValues instead of object
Update changelog.md