IO loaders

[technoweenie]

This adds new loaders for io.Reader and io.Writer objects.

Validating an http request body:

reqLoader, body := gojsonschema.NewReaderLoader(r.Body)
obj := &someObj{}
err := json.NewDecoder(body).Decode(obj)
r.Body.Close()
assert.Nil(t, err)

res, err := gojsonschema.Validate(schemaLoader, reqLoader)
if assert.Nil(t, err) {
  assert.True(t, res.Valid())
}

Validating an http response body:

resLoader, resWriter := gojsonschema.NewWriterLoader(w)
err = json.NewEncoder(resWriter).Encode(someObj)
assert.Nil(t, err)

res, err := gojsonschema.Validate(schemaLoader, reqLoader)
if assert.Nil(t, err) {
  assert.True(t, res.Valid())
}

You can see this in use at git-lfs/git-lfs#1931.