More explicit list of limitations/restrictions on the underlying processes

[chrahunt]

From the README it's not clear what the differences are for a process running normally and under quicken.

What is different:

• the environment, stdin/stdout/stderr, umask, cwd, sys.argv, pid will be different between the execution of the top-level code (e.g., imports, function definitions, global variable definitions) and the execution of the entrypoint
• signals to a quickened process are proxied to the actual process (source)
• the actual app being executed will be a child of the command server, not the users shell
• there may be a long time between execution of the top-level code and execution of the entrypoint (for edample, state retrieved at the top-level of an application may be stale by the time it is used)

What isn't different:

• global changes made from the application entrypoint onward will only exist in that instance of the application

TBD:

• atexit callbacks