Postgres was having trouble restablishing connections for non-pool clients.

Postgres' connector-manager was only checking to see if this.client was null. We
should have been checking for "readyForQuery" status as well. We now make
this.client null if the connection has an error rather than just maintaining
stale information. This is to ensure that we retry our connection until we can
re-establish a firm connection.

This resolves issue #832 https://github.com/sequelize/sequelize/issues/832
Merge branch 'master' into posgres-single-con
Merge branch 'master' into posgres-single-con
Merge branch 'master' into posgres-single-con
Fixed a spec test 'stores the current date in createdAt' since node is async our times might be off slightly by a second or so when doing a comparison.
Merge pull request #845 from durango/posgres-single-con

Postgres was having trouble restablishing connections for non-pool clients closes #832
Merge branch 'master' into milestones/2.0.0