Support aliases

[canac]

Previously for a query containing aliases like

query {
  int1: returnInt
  int2: returnInt
  int3: returnInt
}

graphql-ergonomock would ignore the aliases. You would have to provide a mock like { returnInt: 1 } and the mocked response would be { int1: 1, int2: 1, int3: 1}.

Now for that query, a mock { int1: 1, int2: 2, int3: 3 } yields a response of { int1: 1, int2: 2, int3: 3 } as expected.

Fixes SurveyMonkey#167