Suggest noting the Apache requirement

[designosis]

On a new server environment, I was getting the error Fatal error: Class 'DOMDocument' not found until an excessive amount of googling led me to try running (on Ubuntu) apt-get install php7.1-xml, after which everything worked.

[soundasleep]

That's a good idea. I don't know if it's possible to add this dependency into composer.json - that would be a nice solution. I'll add a note to the README.