Skip send_file to_path spec when run in lint mode

In lint mode, bodies in the specs are converted to arrays, so this
spec doesn't pass in lint mode.

spec/plugin/sinatra_helpers_spec.rb

@@ -392,7 +392,7 @@ def o.each; yield 'Hello World' end
 
     it "returns response body implementing to_path" do
       req[2].to_path.must_equal @file
-    end
+    end unless ENV['LINT']
 
     it 'sets the Content-Type response header if a mime-type can be located' do
       header(RodaResponseHeaders::CONTENT_TYPE).must_equal 'text/css'