GitLab

Also, buffer single-use channels we may walk away from. This was showing
up (rarely) in a go-ipfs test.

per https://github.com/golang/go/wiki/CodeReviewComments#comment-sentences

Finishing adding comments to WantManager and PeerManager, refactor message structure for type
safety, add sending messages test

Seperates the functions of tracking wants from tracking peers
Unit tests for both peer manager and want manager
Refactor internals of both to address synchonization issues discovered
in tests