Fix #70 on rmarkdown's side: read the HTML output using UTF-8

This does not completely fix the problem, and we still need to make a decision
on whether to re-encode the websocket messages with UTF-8, i.e. should this
option be FALSE instead of TRUE by default?

options(shiny.transcode.json = FALSE)
Merge remote-tracking branch 'origin/master' into shiny/encoding
Merge branch 'shiny/encoding'

Conflicts:
	R/shiny.R