Add "entities_count" method

lib/gtfs/source.rb

@@ -72,6 +72,10 @@ def raise_if_missing_source(filename)
       define_method "each_#{entity.singular_name}".to_sym do |&block|
         entity.each(File.join(@tmp_dir, entity.filename)) { |model| block.call model }
       end
+
+      define_method "#{entity.name}_count".to_sym do |&block|
+        count = File.foreach(File.join(@tmp_dir, entity.filename)).inject(-1) {|c, _| c+1}
+      end
     end
 
     def files

lib/gtfs/version.rb

@@ -1,3 +1,3 @@
 module GTFS
-  VERSION = '0.3.0'
+  VERSION = '0.3.1'
 end

spec/gtfs/source_spec.rb

@@ -59,6 +59,16 @@
     end
   end
 
+  describe '#agencies_count' do
+    subject {source.agencies_count}
+
+    context 'when the source has agencies' do
+      let(:source) {GTFS::Source.build(valid_local_source)}
+
+      it {should eq 1}
+    end
+  end
+
   describe '#stops' do
   end