second attempt to get tags correctly linked

[rschrieken]

now that most browsers have unicode regex support. Kept backward compatibility with IE11, including broken behavior.

This is the second attempt to fix https://meta.stackexchange.com/questions/226703/auto-linkification-of-tags-tagname-fails-when-the-tag-name-contains-nonstandard

The earlier PR from Tim is here: https://github.com/StackExchange/StackExchange.DataExplorer/pull/46