Initial commit for branch "dev_check_censusAPIkey" (ndi v0.1.4.9000)

[idblr]

• Fixed bug in reverse dependency check failure for anthopolos() and bravo() functions removing returnValue() when data are not missing
  • Thank you, Roger Bivand, for the catch. Relates to ndi Issue #5
  • Updated duncan(), gini(), krieger(), messer(), and powell_wiley() for consistency in messaging when data are not missing
  • Updated tests for anthopolos() and bravo() if Sys.getenv("CENSUS_API_KEY") != ""