v0.3.1

Adds various new features for table manipulation and the use of a child table for table join operations and other uses.

Changes

• Added ability to create sub/child table
• Merge, concat operations with sub table
• Removed row/col buttons from toolbar to prevent clutter
• Added filtering using string queries; pandas query()
• Rendering and handling of empty tables
• Added clear table button
• Can now hide plot viewer in dataexplore app
• Fix to relative imports