Simplesam

What's Changed
* Merge pull request 22 from mdshw5/develop by mdshw5 in https://github.com/mdshw5/simplesam/pull/24
* Add pileup script and move tests to Github Actions by mdshw5 in https://github.com/mdshw5/simplesam/pull/25
* Add description of pileup.py to README by mdshw5 in https://github.com/mdshw5/simplesam/pull/26


**Full Changelog**: https://github.com/mdshw5/simplesam/compare/v0.1.4.0...v0.1.4.1

Add support for appending to existing SAM files (21). (thanks xizhihui )

- fixes an issue with StopIteration in a generator for python 3.7 (20)

- Minor fix for `Sam.coords` documentation (19)

- `Sam.tags` is now available immediately after object initialization. Previously `Sam.tags` evaluated as `None` unless a call had been made to `Sam.__get__` or `Sam.__set__`. (16)

- Added better support for SAMv1.4+ CIGAR operations (thanks bede)
- Added `Writer.close()` and `Reader.close()` methods (12)