Update Gemfile with newer ruby version.
Reinstate MORE tags for upcoming correct approach.

Revert "Kill all MORE tags to split posts, as they break HTML in every way when paginating (return to full homepage articles)."

This reverts commit 5ae3a5c8da97990b292eb2b9998eb017851fc163.
Fix articleSummary to use raw content rather than compiled one for the split. This avoids breaking the HTML on the paginated posts.