fix(identify) error handling

* handle subroutine errors
* further specify the type of channel
refactor(swarm) specify direction of secure chans
refactor(identify) extract hello
chore(identify) move private func to bottom of file
refactor(identify) extract proto encoding
refactor(identify) pass context to handshake
refactor(identify) keep only minor fixes
Merge pull request #63 from jbenet/fix/identify-test_handshake-issue-61

fix(identify) Handshake