* Update example datasets w/ pbmc3k and tabula muris
* Add `prepare` overview and example
* Add S3 data links
* Incorporate PR feedback & copyedits
* Switch to letter pointers
* unix line endings
* path
* Add numeric inputs for percentiles
* Define initial values for percentile cutoffs in world reducer
* add percentil to crossfilter dimensions
* worldEqUniverse now handles cloned worlds
* add Dataframe.mapColumns
* Wire up handlers for percentile inputs
* World reducer and stateManager know about continuousPercentileMin/Max
* Create world as universe clone (not pointer) to avoid clobbering vals
* Define basic actions for setting continuousPercentileMin/Max
* Under the hood, deal with percentiles between 0 and 1
* Move percentile inputs to visualization settings menu
* Fix padding for undo/redo buttons
* Trigger world rebuild from percentile actions
* BROKEN - pseudocode for clamping dataframe by percentiles upon world rebuild
* fix error handling on clip quantiles; start world clipping implementation
* more unclipped reorg
* rename crossfilter.percentile to quantile
* simplify schema access
* update continuous legend when scale changes
* update color cache when clip changes
* clip obs annotations and var data when clip quantile changes
* use own fromEntries
* fix tests
* stable non-finite float sort/search
* clarify comments
* fix syntax typo
* use new stand-alone clip
* clip expresssion data
* add select tests for non-finite scalars
* basic styles
* clip UI now requires explicit commit
* reset enable/disable accounts for clip percentiles
* better error messages
* fix bug in undo interaction with programatic min brush selection
* small refactoring
* support clipping of int data
* do not perform unnecessary summarizations
* improve caching of dataframe compiled columns
* add percentile precompute to Dataframe.summarize
* use Dataframe.summarize for clip percentiles
* remove obsolete quantile code from corssfilter
* histogram scale and label Y axis, add unclipped X range labels
* layout tweaks
* scatterplot now updates when clip changes
* improve comments
* remove debugging comment
* rework clip number entry validation for usability
* ui tweaks to histogram colors and layout
* enable undo/redo for clip user action
* refine UI on clip value entry
* api cleanup
* update confusing comment
* clarify purpose of isValidDigitKeyEvent
* fix misleading comment
* apply appropriate button-group classes; do not mix span and div
* variable name and comment changes suggested in PR review
* rename sort to sortArray; remove unused and dead code path
* naming changes suggested in PR review
* code review improvements for clarity
* more small changes from PR review
* lint fixes for PR review
* fix spelling error
* clarify that function performs in-place modification of world
* add comment to clarify intent of range operation
* fix bad indents in comments
* clean up __columnsAccessor comments and code
* improve comments around clipPredicate
* field name consistency
* improve comment on quantiles params
* Calculate QC metrics
* Add QC metrics to prepare section of readme
* Add pointer to scanpy qc metrics function
* Don't explicitly pass qc flag as arg
* Add explicit toggle for run-qc/skip-qc
* Move qc metrics calculation to separate step/function
