Check for proper DOI in doi2url
Check for proper DOI in doi2url

This checks for the expected '10.' in DOIs; other values just get a
leading 'http://', in hopes that they are other URLs without a scheme.

@mtholder, please take a look at these changes and let me know if this
is unexpected behavior.

mtholder/peyotl,OpenTreeOfLife/peyotl,mtholder/peyotl,OpenTreeOfLife/peyotl