Use jekyll-commonmark-ghpages 0.1.4 or later
Before:
gem "jekyll-commonmark-ghpages" was resolved to jekyll-commonmark-ghpages 0.1.0.
The older version of jekyll-commonmark-ghpages raise exception when processing frozen string.
After:
The newer version of jekyll-commonmark-ghpages 0.1.4 or later fixes the following error:
Conversion error: Jekyll::Converters::Markdown encountered an error while converting '_posts/2010-11-19-index.md': can't modify frozen String: "-"