Add serialization for supported formats
supported formats fetched on page load: client side work & tests
ihat_supported_formats: should it fail if no iHat URL?
Move test from paper.edit test to paper test
provide test environment with valid ihat JSON
fix rubocop problems
spec_helper.rb: stub ihat formats in test
mock_server: add /formats; no more 404s in other tests
Tahi has is error-free when IHAT_URL is unset