assigned L.geoJson to var geojsonLayer for ability to resetStyle on mouseout

see http://leafletjs.com/examples/choropleth.html for example usage.
especially used in line 51 of example10.R
added html_sub argument to renderMap for being able to use a preloaded javascript variable as the geoJson spec.features

otherwise takes way to long to round trip between R and javascript.
Added Shiny example app leaflet_chloropleth.
generalized Shiny app example leaflet_chloropleth
added Leaflet mapOpts for specifying options like worldCopyJump = TRUE

in order to repeat a copy of the data layers when panning outside
initial globe extent (< -180, > 180). see all options at
http://leafletjs.com/reference.html#map-options
commented out debug line
Merge pull request #317 from bbest/master

assigned L.geoJson to var geojsonLayer for ability to resetStyle on mous...