Implement checking JSON response bodies in the cukes
Update the health feature to properly parse/compare JSON with the new step
Implement the processTemplate() helper method for rendering mustache templates in cukes

This makes it possible to write API docs/acceptance tests using "{{foobar}}"
placeholder values that are generated at runtime for things like timestamps or
auto-incrementing IDs

Very similar to the approach we use for our Cucumber/Ruby acceptance tests via
the lookout-rack-utils gem: <https://github.com/lookout/lookout-rack-test>