add a link to https://gist.github.com/yihui/3422133 to preview all themes
make sure grDevices will always be loaded
fixes #846: the call info will be printed in warning and error messages if available
fixes #844: when x is a numeric matrix, applying format() on it will turn all numbers into the same number of digits
see if I can fix @AlexanderSommer's issue reported at #37; at least it should be easier to diagnose the issue now since I will try to write out the log file
suppress the rgl warning
the correct fix to #704: always append the figure number to label in fig_path(), even when there is only one figure

also closes #832, and closes #579

oh, the universe will probably fall apart due to this change... finger crossed...
a slightly more elegant way to call fig_path()
update examples
roxygenize
add ... to kable_html() to fix the potential problem in Kmisc (sorry, @kevinushey) because the `output` argument has been removed from kable()

basically ... will ignore the output argument
in case of errors, setwd back before writing the incomplete output
make sure opts_knit$get('base.dir') only applies to plots; previously it will also apply to chunk hooks, which was not what I really meant
fix a wrong example in fig_path()
bump version