Move-toward-Jun2018-GraphQL-spec

This release moves us close to the Jun2018 specification, but it also breaks backwards compatibility in a couple of areas as a result.

Stability Release

• 0.9.0 - Stability update:
  • Lager is not a dependency anymore. The library is completely
    independent of anything but kernel and stdlib now.
  • jsx is only used for testing
  • POTENTIAL INCOMPATIBILITY: Error messages reported the path in the
    query in the wrong order (bottom-up. The right order is top-down).
    This was fixed (@gausby)
  • Build is now on Travis CI
  • The dungeon tests now use the schema parser to test it more.
  • Fix: Correctly handle the case where a query document contains one
    operation. In this case, we can implicitly deduce the client wants
    to call the (single) operation. This brings us into convergence
    with the spec.
  • Erlang/OTP 19.3 and 20.0 support
  • POTENTIAL INCOMPATIBILITY: The error reporting system has been
    streamlined and now properly tracks errors in the same way all
    over the system. This paves the way for even better error handling
    in the future, but clients who already rely on the erroneous
    behavior needs to change. Hopefully, the new structure is more
    consistent, so the work of handling errors should be simpler in
    the client.
  • POTENTIAL INCOMPATIBILITY: If the backend provides an Int in
    a Float context, then the integer is automatically converted
    into a float
  • Enumerated types are now supported in the same way as Scalar types
    (work by @CallumRoberts). The feature has not been extensively
    documented yet since it was subject to change, but if your system
    relies on Enumerated types, the code changed around it. The
    feature was somewhat "experimental" since it lacked documentation.
    It still needs an example of its use in the tutorial.