Spotting validation errors is hard without indenting.

This commit does several things:

1) It uses indenting on the source HTML to make it easier to read
2) It adds a correct doctype/content-type
3) Removes the invalid extra closing div tag on this line:
https://github.com/rjw1/randomness/commit/42a13ed78aace0123414b2660b070913500fee14#L0R20