Import Arduino.h rather than Stream.h

[soundanalogous]

Per this note in the Steam.h header file. I'm still trying to understand what led to this change on the Arduino side. Apparently Arduino is using a common core library and if you try to compile against an board from one of the 4 cores referenced in the readme, then you'll get an error regarding Stream.h not being found. Changing to Arduino.h per the note in the Stream.h header seemed to have resolved the issue. Not sure yet if there are other potential issues to be aware of per these changes.

[soundanalogous]

To repro the error I encountered, install the Arduino megaAVR boards package from the Boards Manager, then try to compile StandardFirmata (latest version in the master branch).

[zfields]

By not including the full Arduino dependency, FirmataMarshaller can be ported to other C++ environments beyond the Arduino (e.g. Linux, RemoteWiring, etc.). If we include Arduino.h, we bring in all the dependencies of Arduino.

My original intention for FirmataMarshaller was to solely generate our byte protocol. Theoretically, it should not require a dependency on Arduino to arrange bytes into, or out of, our protocol.

Instead of solving it this way, let me see if I can drop the #include <Stream.h> statement altogether, by simply using a pointer in the public API, and forward declaring the class.

[soundanalogous]

Sounds good.

[zfields]

Okay, I did a little research this weekend. Unfortunately, my quick fix will not appease the compiler, or address the larger problem of deprecation.

I propose that we leverage an interface to Stream, and/or use dependency injection. Unfortunately, doing so will break the FirmataMarshaller public API. Although, I don't really think we make guarantees about it, but I do believe people are using it.

Not only can we not support the megaAVR boards, but Arduino is forcing our hand with the deprecation of Stream. We definitely need to do something. @soundanalogous What are your feelings on breaking the FirmataMarshaller public API, specifically the .begin(Stream &s) method?