Named fragments don't work with mutations

[Poincare]

For example, something like this won't work correctly:

mutation {
  createAuthor(firstName: "John", lastName: "Smith") {
    ...authorDetails
  }
  fragment authorDetails on Author {
    firstName
    lastName
  }
}

because the mutate method within QueryManager works with the mutation OperationDefinition rather than the Document containing the mutation. Should be an easy fix - see PR #251 since that's pretty much the same thing but for queries.

[helfer]

good catch!

[Poincare]

Fixed w/ PR #274.