DOI extraction seems to fail on DOIs with parentheses

[bcampbell]

eg:
doi:10.1016/S0140-6736(12)61426-3
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2812%2961426-3/abstract

The "Add Source" Works OK if you paste in a dx.doi.org url with urlescaped url, but fails if parens are not escaped.