Update error wording

We are no longer exclusively using yml for config. Update the wording of the
error message to reflect this.

lib/active_record_shards/connection_switcher.rb

@@ -138,7 +138,7 @@ def current_shard_id
 
     def shard_names
       unless config = configurations[shard_env]
-        raise "Did not find #{shard_env} in configurations, did you forget to add it to your database.yml ? (configurations: #{configurations.inspect})"
+        raise "Did not find #{shard_env} in configurations, did you forget to add it to your database config ? (configurations: #{configurations.inspect})"
       end
       unless config[SHARD_NAMES_CONFIG_KEY]
         raise "No shards configured for #{shard_env}"
@@ -155,7 +155,7 @@ def switch_connection(options)
       if options.any?
         if options.key?(:shard)
           unless config = configurations[shard_env]
-            raise "Did not find #{shard_env} in configurations, did you forget to add it to your database.yml ? (configurations: #{configurations.inspect})"
+            raise "Did not find #{shard_env} in configurations, did you forget to add it to your database config ? (configurations: #{configurations.inspect})"
           end
           unless shard = config['shard_names'].include?(options[:shard])
             raise "Did not find shard #{options[:shard]} in configurations"