Piping and MQTT.js about primus

[3rd-Eden]

@mcollina It does support piping of data as seen in this example: https://github.com/3rd-Eden/primus/blob/master/example/index.js#L67-L69

The Spark inherits from the stream module: https://github.com/3rd-Eden/primus/blob/master/spark.js#L39 which should provide the pipe method.

If the client is run in Node it will also inherit from the stream interface: https://github.com/3rd-Eden/primus/blob/master/primus.js#L221-L254

If the client is ran through browserify, it "should" also include the stream interface, but I've not tested this as I'm a browserify nub.

[mcollina]

Ideally you should add it to the method list in the README, so you can avoid this dumb question from me :P.

[3rd-Eden]

@mcollina dump questions are always encouraged as they point out flaws in the documentation.