Default dialect in sequelize generatec config

The config.json generated by sequelize -i does not supply a dialect
key/value pair when generating. It defaults to mysql so lets make this
clear by adding it to the config file
Make the logic for manipulating sqlite data types a bit more solid
Merge pull request #1058 from janmeier/sqliteweirdness

Make the logic for manipulating sqlite data types a bit more solid
Merge pull request #1056 from pbjorklund/default_config

Default dialect in sequelize generatec config