fastjsonschema implements validation of JSON documents by JSON schema. The
library implements JSON schema drafts 04, 06 and 07. The main purpose is to
have a really fast implementation. See some numbers:

- Probably most popular jsonschema can take up to 5 seconds for valid inputs
  and 1.2 seconds for invalid inputs.
- Second most popular json-spec is even worse with up to 7.2 and 1.7 seconds.
- Last validictory, now deprecated, is much better with 370 or 23 milliseconds,
  but it does not follow all standards and it can be still slow for some
  purposes.

With this library you can gain big improvements as fastjsonschema takes only
about 25 milliseconds for valid inputs and 2 milliseconds for invalid ones.