Add current reference text and DOI to popup.

This allows easy comparison of current vs. proposed reference text and
DOI/URL in our CrossRef popup. Addresses #376.
Merge branch 'master' into DOI-lookup-with-comparison
Text cleanup (per @jar398's suggestion)

See https://github.com/OpenTreeOfLife/opentree/issues/376#issuecomment-57717840
Merge pull request #470 from OpenTreeOfLife/DOI-lookup-with-comparison

Add current reference text and DOI to CrossRef popup.