Sequelize default ports

[ljupchokotev]

When using dialect: "postgres" and not specifying a port in the options, sequelize defaults to MySQL default port (3306) and gives out a ECONNREFUSED error. This causes a lot of confusion. I think the decision for the default port should go to the connection managers, so when you are using postgresql it will default to 5432 and will not give out a ECONNREFUSED error.