Updates for bytestream reading, add faser-common as a submodule

We should probably discuss this update before merging. Adding faser-common as a submodule requires people to add this by hand (which is fine) but it also breaks CI on your calypso fork if you don't also have a fork of faser-common in the same place. I have updated the README file with instructions, but it would be worth someone else trying this out.

There are also currently permission problems on faser-common (only members of the project can access it) but I think this will be fixed shortly.