use IE8-compatible events; turn off highlighting in IE8
when searching is turned on, we need to make sure the filtering indices `i` are smaller than nrow(filtered data) instead of original data

this fixes the bug reported at https://groups.google.com/forum/#!topic/shiny-discuss/xk2Gh7KJQBM
fix browser height detection and CSS on IE8
fix Markdown content extraction on IE8
Merge pull request #402 from rstudio/bugfix/ie8-compatibility

Bugfix/ie8 compatibility
install some R package dependencies through apt-get instead of R to save time
bug fix: when evalOptions is of length 1, toJSON() converts it to a scalar; we need to use I() to make sure it is always a vector so that we can later $.each()
klutometis/roxygen#191 has been fixed, so no longer need explicit @usage