http://mbmccormick.com/2011/10/ditching-wordpress-for-jekyll-and-github/
use \caption{} and \label{} in latex; use in HTML; use
in markdown
From the options manual: eval.after: (NULL) a character vector of option names; these options will be evaluated after a chunk is evaluated, and all other options will be evaluated before a chunk (e.g. for chunk option fig.cap=paste('p-value is', t.test(x)$p.value), it will be evaluated after the chunk according to the value of x if eval.after='fig.cap')
What about table references?