Support Pandoc 2.11

[cderv]

Pandoc 2.11 introduced this new latex environment while introducing new --citeproc argument (jgm/pandoc@e0984a4#diff-64a9e5fa4509dce2699276c9e39993b4474e2446c3e86941a2f78a379f8c4079)
This follows a previous change we made when Pandoc 2.8 went out (ee529ad).

This PR aims to close #333

See #333 (comment) for some thoughts about the solution

[yihui]

Not sure what's going on with Travis, but the changes look good to me. Thanks!

[cderv]

the changes look good to me.

Great, so we go with the easy way and not conditional on pandoc version. Templates will have the cslreferences environment define for nothing with Pandoc 2.11+ but I guess it does not hurt

Not sure what's going on with Travis

I think it fails because of newer latex that causes issues with some articles. For now we have two problematic, and one of the issue cause pdflatex to hang and I guess this is happening on travis.

Some PR will fix this normally. Will see.

Otherwise, we should use an older binary release of TinyTex until it is fixed.

[cderv]

You've merged the PR that should fix one of the issue (0e83351)

But as TinyTeX is cached on Travis I am not sure which version will be used at some point in master. I know it reinstalled it for checks in this PR. I am bit lost with TeX Live version in our CI workflow - it seems it is cached and so we test on older version that people could encounter.

[cderv]

Forget what I said above, in fact in fails because of #329 - so I guess that is a good sign because now our CI workflow is seeing the issue.

[yihui]

You are correct. I just committed 1054e2b and let's see if it works.

[cderv]

I applied the same fix as in copernicus by pinning only the Tex package that is the culprit. We may not need to pin down the all TinyTeX.