Add the TCP window parameter

[athwds]

I've added code to make TCP window a parameter. Can you open up your repository to let me contribute?

[ndfred]

Thanks for contributing @athwds!

The way this usually works is:

• you fork the repo on your own account
• you make the modification
• you create a pull request out of that (there is a button for that on the github website)
• I can then review it and merge it once we agree on the improvements

As to this improvement, I would love to see a documentation entry for this new parameter and suggested values. I have never had to modify the window size, and I bet few other people have, so doing a bit of hand holding would be nice.

For iOS UIs I also tend to simplify the interface and avoid numeric values (see the other parameters), I would do that too here.