feature suggestion: component reload policies

While developing here I'm noticing that I'm having to manual reload a lot (mostly by renaming the card that I'm working on). I saw what you said about data reloading at the issue #15, but at same time, when you change data on your video demo it reloads (there you are using Sablono, not sure if it matters).

I noticed my cards only get re-render if I interact with then or remove/add/rename, and I think the workflow could be much better if they just re-render all the times when reloading (or maybe even on a render loop).

I propose that we have some sort of settings for how to deal when code updates, it could be an extra key at the configurations like `:reload-policy`, and here and some ideas for values of it:
- `:none` - this is like the current one, the component doesn't re-render on code reload
- `:render` - just re-render the component keeping the state (the props on the atom)
- `:refresh` - render all over again with the data on code (discard current state)

So we could write:

``` clojure
(defcard-om sample-om-card
component
{:data 1}
{}
{:reload-policy :refresh})
```

These are just ideas to deal with the problem of having to manually reloading the cards against code changes, please let me know your thoughts/ideas on that matter.

Thanks.