Complexity algorithm should work with fragments

[evanmcneely]

Get fragment tests to pass

[shalarewicz]

Added tests for fragments in #75.

To close this issue both fragments and inline fragments should be handled.

[shalarewicz]

We will need to reassess how fields are stored for union types. Currently, the typeWeight object does not store any fields directly on the union type. Instead all fields are stored on the type comprising the union type. When analyzing complexity inline fragments are used do differentiate between fields unique to one or more of the types in the union. We should be able to use the type specified in the inline fragment to resolve this field.

However for types that are common to the all types in the union, they complexity algo will search for the field on the Union type which currently throws an undefined error. In the below case heroUnion resolves to SearchResult which is a union of Human and Droid types. The below query throws and undefined error when getting the complexity of name which does not exist in the list of fields for SearchResult on the typeWeight object

 query {
  heroUnion(episode: EMPIRE) {
    name
    ... on Droid {
      primaryFunction
    }
    ... on Human {
      homePlanet
    }
 }
}

A potential approach would be two look for common fields when we parse the schema and add these to both the Union type SearchResult and the individual types Droid and Human.

@evanmcneely we identified this as an issue earlier. Thoughts?