split long lines of js input for node.js to avoid tty issues

[joemarshall]

This fixes issue #139 . It would be nice to get it merged so I can test node.js in urllib3

[joemarshall]

Hmm, it seems to break a couple of tests. I'll look at it later.

[joemarshall]

Hi @ryanking13 if there's any chance you could look over this - I'd like to merge it soon because it is needed for urllib3/urllib3#3427 to pass testing.

Basically rather than relying on the tty that node is running in to accept super long lines, it instead splits the lines sent to node.js into shorter lines and reassembles them at the node end.

This is needed because in nox tests in urllib3, it is running inside a subprocess, so the change to the tty doesn't affect the subprocess stdin/out, and instead affects the outer tty.

[ryanking13]

Thanks @joemarshall. I left some minor comments about the readability for future readers of this code. The feature-wise looks good to me. So feel free to merge and release after resolving my comments.