Added support for black autoformatting

Author: syrusakbary

.travis.yml

@@ -4,17 +4,18 @@ dist: xenial
 sudo: true
 
 python:
-  - 3.6
-  - 3.7
+    - 3.6
+    - 3.7
 
 install:
-  - pip install pipenv
-  - pipenv install --dev
+    - pip install pipenv
+    - pipenv install --dev
 
 script:
-  - flake8 graphql tests
-  - mypy graphql
-  - pytest --cov-report term-missing --cov=graphql
+    - flake8 graphql tests
+    - black graphql tests --check
+    - mypy graphql
+    - pytest --cov-report term-missing --cov=graphql
 
 after_success:
-  - coveralls
+    - coveralls

Pipfile

@@ -5,6 +5,7 @@ name = "pypi"
 
 [dev-packages]
 graphql-core-next = {path = ".", editable = true}
+black = "*"
 flake8 = "*"
 mypy = "*"
 pytest = "*"