Install Black code-formatter for Python

tildes/requirements-to-freeze.txt

@@ -3,6 +3,7 @@ alembic
 amqpy
 argon2_cffi
 astroid==1.5.3  # pylama has issues with pylint 1.8.1
+black
 bleach
 click
 cornice

tildes/requirements.txt

@@ -1,12 +1,14 @@
 ago==0.0.92
 alembic==1.0.0
 amqpy==0.13.1
+appdirs==1.4.3
 argon2-cffi==18.1.0
 astroid==1.5.3
 atomicwrites==1.1.5
 attrs==18.1.0
 backcall==0.1.0
 beautifulsoup4==4.6.3
+black==18.6b4
 bleach==2.1.3
 certifi==2018.4.16
 cffi==1.11.5
@@ -78,6 +80,7 @@ SQLAlchemy-Utils==0.33.3
 stripe==2.4.0
 testing.common.database==2.0.3
 testing.redis==1.1.1
+toml==0.9.4
 traitlets==4.3.2
 transaction==2.2.1
 translationstring==1.3