py-crontab: updated to 2.3.8

Version 2.3.8
- Updated RADME and special time setting fixes.
- Attempt a fix of issue 27 (no test suite test)
- Merge branch 'master' into 'master'
- update README.rst file
- Fix 48, specials can't be changed to another time.
- Bump version for pypi update
- Fix 41 dead link to github
- Ignore mypy_cache
- Fix 39 - Tab next to username will parse correctly
- Merge remote-tracking branch 'flotus/patch-1'
- Improve explaination about using the write function
- fixed environment

(adam)