* comment
* add histogram functionality to Dataframe; port category occupancy to use it
* fix binning and create histogram for continous by catagorical
* Remove unnecessary logs
* Begin work on KDE
* Replace broken KDE with working histogram
* Define domain and range based on data from histogram
* Fix occupancy
* Add continuous obs and switch to canvas
* Stop value from always rerendering
* clear before render
* Clear canvas on render
* refactor categorical occupancy to canvas
* Remove log
* simplify finding max
* refactor kde->histogram and occupancy->bins
* refactor svg -> canvas
* rename to occupancy stack
* create popup
* add metadata and categorical values to popup
* fix overflow
* remove zeros info
* style graph
* fix shouldComponentUpdate to look for world changes
* change categorySelected -> categoryValueSelected
* refactor out render
* remove comment
* conditionally have bottom border
* remove diff comp
* remove comments
* remove unnecessary mapping
* Add comments describing drawing functions
* comments
* flip comparison order
* remove logging
* move default to parameter
* move defaults to parameter
* disable popover if not showing histogram
* fix wording and styling
* add line break
* add own range() function
* lodash cleanup
* remove redundant fill range implementations
* remove use of _.get
* sync test babel config with build
* update tests to match new range implementation
* immutable crossfilter
* first cut at reducer refactor with cascade model
* add initial redo/undo implementation
* small optimization
* integrate expression with history
* add tests for new reducers and fix a couple of small initialization bugs
* treat tiny lasso selections as a clear
* better function name for clarity
* fix undo for differential expression
* remove logging
* fix regression due to bad merge
* cleanup and comments for clarity
* improve undoable configuration for flexibility
* fix stale comments
* remove debugging code from production build
* rename categoricalSelectionState
* rename file
* improve comments