Update policy_documents.md

I moved NIH/NCI under HHS, and also suggest removing entirely the link to [http://www.hrsa.gov/healthit/toolbox/HealthITAdoptiontoolbox/OpenSource/]().  If you check out the latter, you will see that it is not very accurate/mature, and should not be used as an exemplar for anything.
Merge pull request #46 from Klortho/patch-1

Update policy_documents.md