Add support for setting mgo.DialInfo

[iamsaso]

This enables tapping into mgo.DialInfo and setting up SSL when needed

Code that I use to enable SSL

config := &bongo.Config{
	ConnectionString: viper.GetString("mongodb.uri"),
	Database:         viper.GetString("mongodb.database"),
}

if viper.GetBool("mongodb.ssl") {
	if config.DialInfo, err = mgo.ParseURL(config.ConnectionString); err != nil {
		panic(fmt.Sprintf("cannot parse given URI %s due to error: %s", config.ConnectionString, err.Error()))
	}

	tlsConfig := &tls.Config{}
	config.DialInfo.DialServer = func(addr *mgo.ServerAddr) (net.Conn, error) {
		conn, err := tls.Dial("tcp", addr.String(), tlsConfig)
		return conn, err
	}

	config.DialInfo.Timeout = time.Second * 3
}

connection, err = bongo.Connect(config)
if err != nil {
	log.Fatal(err)
}

[coveralls]

Coverage decreased (-0.05%) to 83.182% when pulling d40f50c on sasso:master into 0d02692 on maxwellhealth:master.

[coveralls]

Coverage increased (+1.01%) to 84.242% when pulling 53f6a19 on sasso:master into 0d02692 on maxwellhealth:master.

[securingsincity]

@Sasso this looks great thanks!