Added 'black' to Travis CI. Also removed old sort-imports.sh tool.

Author: jonathanslenders

.travis.yml

@@ -11,7 +11,7 @@ matrix:
 
 install:
  - pip install . pytest coverage codecov flake8 mypy
- - pip install isort
+ - pip install isort black
  - pip list
 
 script:
@@ -26,5 +26,7 @@ script:
  # When this fails, please run ./tools/sort-imports.sh
  - isort -c -rc prompt_toolkit
 
+ - black --check prompt_toolkit
+
 after_success:
  - codecov