Makes CC a first class citizen with `to` and `from`.

If the adapter doesn't pass along a `to` then it falls back to parsing the headers passed along from the adapter. 

This breaks the current cc a bit in that the default configuration is `:hash` and the current one behaves like `:email`. I think this is maybe ok in that people using the current behavior can update their config to use `:email` and not have any more problems. 

/cc @sauron @natew