Fix taxon data corruption across test runs

* Changes calls to Taxon.iconic_taxa.find_by_name to call
  Taxon.find_by_name instead
Treat Flickr tests as pending with invalid API key
Fix test failure when taxon_spec runs with others

* This spec would pass and fail unpredictably due to whether or not there were
  id collisions between Taxon and TaxonName. This was in turn affected by how
  many times load_test_taxa is called during a test run.
Merge pull request #171 from md5/fix_load_test_taxa

Fix load test taxa