Fast-carpenter

Added
- Support for ND jagged array in expressions, PR 73
- Automatic conversion of ObjectArrays from uproot to JaggedArrays, PR 73

Changed
- Fixed interpretation of user-defined variables for uproot, issue 67, PR 71 [benkrikler](https://github.com/benkrikler)

Changed
- Add changes to support uproot 3.9.1 and greater, issue 68 [benkrikler](https://github.com/benkrikler)

Changed
- Protect against overwriting branches and add tests, pull request 66 [benkrikler](https://github.com/benkrikler)

Added
- Adds support for masking variables in their definition, issue 59 [benkrikler](https://github.com/benkrikler)
- Adds several constants for variable expressions, issue 21 [benkrikler](https://github.com/benkrikler)
- Added this changelog [benkrikler](https://github.com/benkrikler)

Changed
- Use `pandas.groupby(..).counts()` to make binned dataframes, issue 51 [benkrikler](https://github.com/benkrikler)

Removed

Added
- Add support for multiple output file types for binned dataframes, issue 57 [asnaylor](https://github.com/asnaylor)

Changed
- Fix issue with binned dataframe expressions and multiple similar branch names, issue 60 [benkrikler](https://github.com/benkrikler)
- Enable multiple cut-flow stages and make the input chunk.tree have consistent array and arrays methods, issue 61 [benkrikler](https://github.com/benkrikler)

Removed