Squashed 'json/' changes from 0b8c484..9dc2c40

9dc2c40 Ensure that only RFC3339 datetimes are valid.
b4850be Merge pull request #41 from mchiocca/develop
c5c9202 Add json-schema (PHP) to the list of who uses the test suite.
dfa1985 Remove composer.json.
429b872 Add composer.json file for PHP dependency management. - This allows PHP projects that use Composer to include this project as a required dependency.
4eaaea8 Fix for newer jsonschemas.
f61fc0d Make the README not lie.

git-subtree-dir: json
git-subtree-split: 9dc2c40347a8724163461ab553c0fb1adf812f89
Merge commit '0a93c5da6f8db71ded773af1d5609c5f2e6ba241'
Make py.test less stupid.
Show skipped format checkers.
Only allow RFC 3339 date times, not all of ISO 8601.

Closes #115