misc:
* test network client getting more than max
* test for find providers
* rename factory method
* local network
* misc test improvements
* test bitswap get block timeout
* test provider exists but cannot connect to peer
* test sending a message async over local network
> Why expose num bytes sent and received?
Makes it easy to test consistency of the ledgers
> Got a better reason?
Makes it possible to expose metrics to the people-facing API
Move go-ipfs/bitswap package to go-ipfs/exchange/bitswap
* Delineates the difference between the generic exchange interface and
implementations (eg. BitSwap protocol)
Thus, the bitswap protocol can be refined without having to overthink
how future exchanges will work. Aspects common to BitSwap and other
exchanges can be extracted out to the exchange package in piecemeal.
Future exchange implementations can be placed in sibling packages next
to exchange/bitswap. (eg. exchange/multilateral)
