find/add data for Golden-winged warbler

[ahhurlbert]

This species was missing from the NA_diet_refs species list.

Although it does not contain diet data itself, this paper points to several others that may have quantitative data:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.957.8841&rep=rep1&type=pdf

e.g. beginning on page 9