Release 0.5.0
Release 0.5.0

This release includes
- Changing output asserts
  - `.prints` -> `.stdout().contains`
  - `.prints_exactly` -> `.stdout().is`
  - `.prints_error` -> `.stderr().contains`
  - `.prints_error_exactly` -> `.stderr().is`
- Add negative output assertions
  - `.stdout().isnt`
  - `.stdout().doesnt_contain`
- Output assertions are now anded together rather than replacing each
  other.

killercup/assert_cli