Logging and JSON

(all addressed towards @mdmoss)

### Logging

Added a small lib under `bark.lib.logs` as a wrapper around the standard Python `logging`. Putting it into its own lib might be an overkill (rather than using `logging` directly), but it feels safer this way.

### JSON

I've rewritten your JSON validation -- we do not have to do type conversions in JSON. Since everything is either a bool, int, float, unicode, or list, it suffices to directly check the type.

That is also safer from the exception-catching point of view. What if something raises an exception that is not `ValueError`? This way, we make Python's internals do all the work instead.

### Requests

Please test all the code you add and modify. For instance, you migrated `/login` to use the new JSON checking, but not `/logout`.

Also, could you *rebase* the `events` branch against `master` after the merge? It keeps the history cleaner. You will have to force-push the events branch, but since no one else has cloned it (yet), it should be fine.