Now, it's 10X faster than [jsonschema](https://github.com/Julian/jsonschema), 40X faster than [schematics](https://github.com/schematics/schematics).

benchmark result in travis-ci:

        json:loads-dumps              1000
  jsonschema:draft3                   180
  jsonschema:draft4                   184
      schema:default                  41
  schematics:default                  51
      validr:default                  2384
      validr:use-refer-merge          2106
  voluptuous:default                  100