IE8 is throwing "Expected ']' in regular expression" (both old and new expression - so this commit did not introduce the issue)  Discussion (and fix) with @tivie [here](https://github.com/showdownjs/showdown/commit/c9e85f129480bf48d9ae064d7d0b476c56452ad4#commitcomment-17785890)
IE8 is throwing "Expected ']' in regular expression" (both old and new expression - so this commit did not introduce the issue)
Discussion (and fix) with @tivie here