Allow refresh to execute 30 times a second maximum

Allow refresh to execute 30 times a second maximum

For commands that pass a significant amount of output to the write function,
this prevents the terminal maxing out the CPU and making the UI unresponsive.
While commands can still run beyond what they do on the terminal, it is far
better with a debounce in place as every single terminal manipulation does not
need to be constructed in the DOM.

A side-effect of this is that it makes ^C to interrupt a process seem more
responsive.

Fixes #127
Fixes #126