Only send form fields that have been populated

Not familiar wirh Coffeescript or Node.js, also not great at Git, so my apologies if I have not 'pulled' this correctly.

What I wanted to change was to only submit those form fields that have values.  The current behaviour is that when I press 'Try it out' form fields that I have not edited are submitted with the value 'undefined'.  This does not make my service very happy.  So I put in an IF to check that the property has some value.