Amp Future instances double both as Promisor and Promise
implementations when AMP_DEBUG is defined and set to false.
This switch allows private Promise resolution safety by
default at the expense of performance.
Amp applications should set AMP_DEBUG to false in production
environments to maximize performance.
This commit removes the Combinator and Resolver classes altogether.
The relevant functionality is now concentrated entirely in the
analogous functions:
- all()
- some()
- any()
- first()
- map()
- filter()
- resolve()
Additionally, all Promisor implementations now *require* a Reactor
upon instantiation. Previously this parameter could be null and the
static singleton reactor instance would be used automatically.
