logger: don't rely on console.log; use process.stderr instead
bump version
base_service: remove `error` state,
  now states are `closed`, `connecting` and `connected`
  fix invariants
util: tweak `makeError`'s default message
client: introduce `Stateless` service, that is capable of automatic
  reconnect and of rerequesting pending sessions when connect succeeds
  at some point
client: implement locator client, using Stateless class
client/locator: correct signature of `resolve` method
client/service: implement re-resolving stateless and stateful clients
base_service: reset sessions if clearSessions requested
client/resolving: prepare to support stateless flag for resolving client
util: add linkProtoProps utility function
  to be used for linking descending classes' errorHandler dicts
implement ErrorEmitter class
make use of ErrorEmitter in clients
Merge branch 'feature/client-improvements' into v0.5
bump version