input_select: default to selectize=F so that iframes don't expand downward

When selectize.js is updated with the ability to open upward, we can
switch back to selectize.
layer_lines: don't auto group by x and y. Fixes #171
Update test specs
Get scale name correctly
add_scale_info: get scale from info object
Set default axis labels in layer_histograms. Fixes #175
Set default axis labels for various layers
Update test specs
Merge pull request #176 from rstudio/axis-labels

Set default axis labels in various layers. Fixes #175
Make layer_bars symmetric about tick marks
layer_bars: use auto_group
Update demos
More demo updates
merging in rstudio/master -- one conflict repaired in layer_bins.R

Merge remote-tracking branch 'rstudio/master'

Conflicts:
	R/layer_bins.R