first pass on composable CPs
wip; hackin @twokul @hjdivad
wip;

- works with ember objects
- doesn't work with POJOs b/c we use reopen
- maybe works with array computed

TODO
- kill ccomputed; move everything to regular computed
- test array computed
- make it work with POJOs
wip;

TODO
- test array computed
- make it work with POJOs