regex option to highlight classes and id's when they start at the beginning of tag

Hello, thanks for hamlet mode. I've been using it quite frequently.

In hamlet, writing the 'div' tag name is optional. So `<div .class>` and `<.class>` are the same thing. Currently hamlet-mode doesn't highlight classes and id's when they start at the beginning of a tag. I added an optional match for the `<` character before `[.#]` in the regexp so it will catch and highlight these cases.

I tested this on several of my hamlet files, but let me know if you think there's a better way to do it!