Implement `has_file' condition keyword

lib/producer/core/tests/has_file.rb

@@ -0,0 +1,11 @@
+module Producer
+  module Core
+    module Tests
+      class HasFile < Test
+        def success?
+          env.remote.fs.has_file? arguments.first
+        end
+      end
+    end
+  end
+end