Restructure and clean up lookup tests.

Rakefile

test/services_test.rb

test/unit/active_record_test.rb

test/unit/cache_test.rb

test/unit/calculations_test.rb

test/unit/configuration_test.rb

test/unit/custom_block_test.rb

test/unit/error_handling_test.rb

test/unit/geocoder_test.rb

test/unit/https_test.rb

test/unit/ip_address_test.rb

test/unit/lookup_test.rb

test/unit/lookups/bing_test.rb

test/unit/lookups/dstk_test.rb

test/unit/lookups/esri_test.rb

test/unit/lookups/freegeoip_test.rb

test/unit/lookups/geocoder_ca_test.rb

test/unit/lookups/geocodio_test.rb

test/unit/lookups/google_premier_test.rb

test/unit/lookups/google_test.rb