cleanup: remove traing whitespace and tab to sapce
Merge pull request #973 from sunglim/nit_cleanup

cleanup: remove traing whitespace and tab to sapce
Rename files under widgets/examples ('-' -> '_')
Further file renaming
Further example fixes
Fix and expand spark-splitter example
Finish spark-split-view example
Merge pull request #980 from ussuri/update-widgets-examples

Update widgets examples