A quick update for those who are interested and don't follow me on Github, I wrote this tool for people like me who write a lot of HTML/CSS at their jobs, and especially have to present those templates as deliverables. A lot of the times you're only responsible for the frontend development, so it's hard to get the benefits of server-side web development. In other words, you have to repeat yourself a bunch of times as you're coding, and it starts to get messy. I just hacked together something using XML and PHP to keep the content separate. There's not much separate documentation, just inline comments, but the tool is definitely usable (especially by those who understand basic PHP). A demo, also in progress, can be seen here.