Use lookup indicated by test file.

test/unit/lookups/pelias_test.rb

@@ -23,7 +23,7 @@ class PeliasTest < GeocoderTestCase
   end
 
   def test_query_for_reverse_geocode
-    lookup = Geocoder::Lookup::Mapzen.new
+    lookup = Geocoder::Lookup::Pelias.new
     url = lookup.query_url(Geocoder::Query.new([45.423733, -75.676333]))
     assert_match(/point.lat=45.423733&point.lon=-75.676333&size=1/, url)
   end