Fix build error.
Fix build error.

Conversion error: Jekyll::Converters::Markdown encountered an error while converting '_posts/2016-10-30-learning-elm-part-1.md':
                    Rouge::Guesser::Ambiguous
jekyll 3.6.2 | Error:  Ambiguous guess: can't decide between ["diff", "mosel"]

k4ml/k4ml.github.io,k4ml/k4ml.github.io,k4ml/k4ml.github.io,k4ml/k4ml.github.io