DEV: Adds the ability to use config files instead of passing long lists of
commands.

Users may now put a .qdb in the cwd and/or in their home to create
a configuration to pass to Qdb when it is started.
BUG: Fixes the qdb-cli's handling of exceptions that are raised in the
program.
DEV: Update pyflakes and flake8 requirements.
BUG: Fixes a race condition in the removal of dead clients by adding an
RLock.
DEV: Cleans up the reprs for the servers to not be recursivly defined.