(78863100) Username alphanumeric/underscore validation

Hmm interesting... I'm still learning about how all this git forking works, but it seems to have combined my last two commits. If that's the case, then this is regarding:

1) darkening edit/delete buttons
2) validation on alphanumeric/underscore usernames

@netikular, @jlebensold, @grayden guys, whoever decides to merge this, please check the validation one (esp. to make sure the regex looks good. I also looked into validates_format_of for security holes or anything and it looks clean :+1: )