Broken Middleman 3 code

[matiaskorhonen]

The code for Middleman 3 appears to be broken, there's a mismatched end tag and even after removing it I can't get the code to work.

[multiscan]

In fact you're right, the final "end" tag should be removed: it was the "end" corresponding to "helpers do" that you should already have in your config.rb.
In any case the code should included in the helpers space:

helpers do
# PASTE THE CODE HERE
end