allow Fixture to be a ContextManager

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
0.7.0: Fixture loads config from dirs

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
0.7.1: add terminal control sequence handling

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>