Fields created in transformRecordHook can't be used by other config options

[crccheck]

Because transformRecordHook comes at the end of processing, if you create a new field there, you can't use it for typeField or indexField, etc. I'm not sure if moving it up would create a chicken/egg problem.

dynamo2es-lambda/lib/handler.js

Lines 76 to 78 in 88d43e9

	if (options.transformRecordHook) {
	doc = options.transformRecordHook(doc, parsedRecord.OldImage);
	}

[iamdavidmartin]

Yeah, this would be super helpful. or this pull request: #40.