v0.5.0

Breaking Changes

• Query::body no longer exists, the Query itself is now directly
  serializable, and exposes the query type itself. Errors that were
  previously exposed by Query::body() will now be surfaced when serializing a
  Query.
• Argument::new has been updated to take a SerialiableArgument itself.
• Removed selection_set::Error.
• SerializableArgument::serialize & Scalar::encode now return
  Box<std::error::Error> errors rather than ()

Bug Fixes

• cynic-codegen will now build with the rustfmt feature disabled.
• Removed some unwraps that I lazily put in and forgot to remove.