Consider non-hyphen category format

[MaxGhenis]

Since categories are currently in the URLs, the standard defined in the README is to use lowercase and hyphens, e.g. demo-days. If we remove them from the URLs, it'll only matter for the tag pages, e.g. if we wanted to make demo-days -> Demo Days, http://blog.pslmodels.org/categories/#demo-days would become http://blog.pslmodels.org/categories/#Demo%20Days. The tag might be more readable in the post itself in this case, as it's visible like below.