add features to Readme
reimpl validate in terms of validate.result instead of the other way around
(it's clearer which is the sugar method this way)
fix context.validSchema() when multiple anyOf conditions valid
  - change anyOf validation to encode all conditions, not just up to the first valid
  - add tests

add validate.use() extension methods onto subcontexts, not just top-level context
version bump (v0.0.5)