cauldron detect updates and reload

[mortbauer]

Hey, first thanks for cauldron, seems quite interesting!

A thing I'm missing which would seem to be logical to be in is some kind of watchdog/watchgod integration. The usecase is that I simple do not wanna leave my editor.
I have seen that there is the possibility to run a step from the cauldron ui, but it would be great to maybe have some --reload option when starting the ui, which then just uses watchgod underneath to reload when it detects a filesystem write.

What do you think? Maybe I could do a pull request even, don't know yet, haven't looked inside the source code of cauldron yet ;)