v1.6.0

## Arrow v1.6.0

[Diff since v1.5.0](https://github.com/JuliaData/Arrow.jl/compare/v1.5.0...v1.6.0)


**Closed issues:**
- A vector with elementtype `Any` stackoverflows `Arrow.write`: (#191)
- Writing an empty DataFrame errors (#194)
- ArrowTypes as standalone package doesn't interoperate with Arrow.ArrowTypes (#209)
- ERROR: type Nothing has no field fields (#210)
- Remove `master` branch (#216)

**Merged pull requests:**
- Rename LICENSE.md to LICENSE (#195) (@simeonschaub)
- Test expected log records (#204) (@omus)
- Use standalone ArrowTypes package (#212) (@omus)
- Set ArrowTypes to version 1.1.0 (#213) (@omus)
- Remove old arrowtypes.jl file (#215) (@omus)
- add metadata to `show` method (#217) (@ericphanson)
- fix writing an empty table (#221) (@KristofferC)
- Set project version to 1.6.0 (#222) (@omus)