upquote must be used after fontenc

otherwise single quotes in verbatim environments will be in trouble; see an example at http://stackoverflow.com/a/12852815/559676
Merge pull request #60 from yihui/patch-1

upquote must be used after fontenc
Load upquote after fontenc in latex template.
latex template:  conditionalize author and date.

Thanks to ivoanjo for the patch. Closes #61.
latex template:  Added fontfamily variable.

Thanks to tlvince for the patch.  Closes #50.
latex template: Added linestretch variable that loads setspace.
Changes made in master Pandoc repo