It now takes two arguments: parent (optional, only for non-root
components) and props (optional). In the case of the root component,
the env is taken from the config (config.defaultEnv). If it doesn't
exists, the default env is created on the fly.
Closes#306
This commit also changes the behaviour of willPatch and patched: they no
longer transfer data from one to the other, because it can be done
cleanly by hooks and a closure.
closes#307
Aaron Bohy