provide implicit Prepend

[mpollmeier]

fix for http://stackoverflow.com/questions/40754229/scala-gremlin-scala-hlists-poly2-rightfold-and-a-missing-implicit-prepend

[prismofeverything]

Hi @mpollmeier, thanks for the PR! This did indeed allow the file to compile, but now that I am writing a test for it I am getting the same error (just in a higher place)! It seems the need for this implicit Prepend is bubbling its way up the stack? How do I avoid this ignoble fate? Is there some bottom to this recursion I can impose?

I updated the repo to reproduce. You can run it with

> sbt test

Let me know what you think, thanks!

[mpollmeier]

moved discussion to https://gitter.im/mpollmeier/gremlin-scala#utm_source=notification&utm_medium=email&utm_campaign=unread-notifications