fix(README): use machine instead of node

Internally we call every member of an etcd cluster a "machine" so stay
consistent when talking in the README.
Merge pull request #342 from philips/use-machine-nomenclature

fix(README): use machine instead of node
fix(README): fix 9 instances of v1

remove references to the v1 API and consistently use the v2 API.
Merge pull request #330 from philips/fixup-readme-remove-v1

fix(README): fix 9 instances of v1
fix(event_history.go) should not scan prefix
Fix spelling mistakes in internal-protocol-versioning.md
Merge pull request #353 from baruch/patch-1

Fix spelling mistakes in internal-protocol-versioning.md
test add watcher prefix test
Merge pull request #352 from xiangli-cmu/fix_watch_prefix

fix(event_history.go) should not scan prefix