Improve status code to use Symfony contants

Use Symfony Response HTTP_ constants in documentation and code.

Return 500 when Unhealthy

Changes the HTTP status code to be 500 when a service is deemed to be unhealthy. This is to improve compatibility with health checking in Elastic Beanstalk.

Make more compatible with psr versions

Change to support >= psr/log 1.0 and psr/container >= 1.1

Early version with JSON API and Console command

• Added simple Json formatter and controller
• Updated example

Early release, console only version

0.0.1

Update Snyk badge after initial scan