Fixing ACS dataSet strings which are coded to URL

The URL was being called with `"http://api.census.gov/data/2010/" + dataSet`, so if `dataSet` is "acs", the URL becomes `http://api.census.gov/data/2010/acs` when it should be `http://api.census.gov/data/2010/acs5`. Changing `dataset` from "acs" to "acs5" fixes the issue in those cases.