Update readme, link to json_schemer

[sandstrom]

Two thoughts:

1. Add a link to https://github.com/davishmcclurg/json_schemer

   Mention that it support the most recent version of JSON Schema.

2. Maybe even consider donating the gem name to that project?

   json_schemer could be re-released as version 1.0.0 or json_schema. The current codebase in this repo could be moved into a frozen v1 branch, kept in this repo.

   Assuming json-schemer would like to change their own project name, obviously. Not sure if it's worth the extra work.

   But your name is a good one, and it would help the ruby community to have a single 'canonical' JSON schema gem.

Just some thoughts though! 😄

cc @davishmcclurg

[davishmcclurg]

Thanks @sandstrom. Similar discussion relating to json-schema gem:

• Join forces with voxpupuli/json-schema davishmcclurg/json_schemer#142
• The future of the JSON schema gem voxpupuli/json-schema#423