Fix docs for ggvisControlOutput
Fix error with zero-row data frames

The error happened when mark_symbol was used with zero-row data frames
transform_bin: don't crash on empty data
Brush: reduce opacity and don't inherit props
Use UTC for all time communication
Remove unneeded export
Correctly get width and height of marks
transform_bin: check that output is data frame
Get DOM element instead of jQuery object
Make sure size is represented as number, not string
Use svg as default renderer in parseSpec
Make sure brush event handlers aren't duplicated
Remove event_handler.R
Update docs with Roxygen2 3.0.0
Add event broker class
Add some sample brokers & new inputs
R plumbing
Fix so handlers now work
Allow handlers to be branch components
Clean up left_right example