regression in links with '@'

[tippenein]

#33 fixed an issue with missed urls using '@' but it seems to have affected other content. For example, linkify will pick up "@some.username" as a link.

It only seems to be the case in linkify-react. The linkify-html passed the test case I entered.

I wasn't able to easily see the differences in the way each processes their input, so sorry this isn't a pull request.

Thanks