doc: add note about discovery proxy
Merge pull request #1320 from jonboulle/proxy_doc

doc: add note about discovery proxy
main: correct peer-addr reference
Merge pull request #1321 from jonboulle/peers

main: correct peer-addr reference
discovery: switch to fake clock
godeps: add clockwork
store: switch to fake clock
etcdserver/etcdhttp: switch to using fake clock
godep: update clockwork dependency