v0.2.1

• Add missing arity (3) in Cols/Rows apply method
• Add cellMap to Column and Series
• Add appendRows and AppendCols to Frame
• Add various other methods to Frame
• Add unzip to Index
• Faster equals for Index
• Add combine and merge to Series
• Add various other methods to Series

Changeset: v0.2.0...v0.2.1