changing binwidth to width in all public facing stuff
bug fixes: params$binwidth, POSIXt -> POSIXct
binwidth -> width
auto doc updates
binwidth -> width
POSIXt -> POSIXct
Merge branch 'master' of github.com:rpruim/ggvis

Conflicts:
	R/compute_bin.R
	man/bin_vector.Rd
	man/layer_histograms.Rd