A few updates given recent changes
More on props/scales
Eliminate process from prop_value.
Closes #27
Fix typo that broke scale overides
Some basic spec tests for scales
Improved datasource docs
More docs for guides
Improve interactive input documentation
Improve mark documentation
Improve documentation for pipe and pipeline
Remove old files
Improve documentation of scale and scales
Better documentation for individual scales
Rename ggvis_scales to scales
Remove outdated range function
find_scales -> add_default_scales
More documentation for shiny connections
Better documentation for by_group and split_df
Better documentation for transform
New interface for by_group