Add initial black formatting (open-telemetry#104)

Closes: open-telemetry#88

.flake8

@@ -0,0 +1,2 @@
+[flake8]
+ignore = E501,W503,E203

.isort.cfg

@@ -1,3 +1,6 @@
 [settings]
-force_single_line=True
-from_first=True
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+use_parentheses=True
+line_length=79

.pylintrc

@@ -65,7 +65,10 @@ disable=missing-docstring,
       too-few-public-methods, # Might be good to re-enable this later.
       too-many-instance-attributes,
       too-many-arguments,
-      ungrouped-imports # Leave this up to isort
+      ungrouped-imports, # Leave this up to isort
+      wrong-import-order, # Leave this up to isort
+      bad-continuation, # Leave this up to black
+      line-too-long # Leave this up to black
 
 # Enable the message, report, category or checker with the given id(s). You can
 # either give multiple identifier separated by comma (,) or put this option

tox.ini

@@ -45,6 +45,7 @@ deps =
   pylint~=2.3
   flake8~=3.7
   isort~=4.3
+  black>=19.3b0,==19.*
 
 commands_pre =
   pip install -e {toxinidir}/opentelemetry-api
@@ -55,6 +56,7 @@ commands_pre =
 commands =
 ; Prefer putting everything in one pylint command to profit from duplication
 ; warnings.
+  black --check --diff opentelemetry-api/src/opentelemetry opentelemetry-api/tests/ opentelemetry-sdk/src/opentelemetry opentelemetry-sdk/tests/ ext/opentelemetry-ext-http-requests/src/ ext/opentelemetry-ext-http-requests/tests/ ext/opentelemetry-ext-wsgi/tests/
   pylint opentelemetry-api/src/opentelemetry opentelemetry-api/tests/ opentelemetry-sdk/src/opentelemetry opentelemetry-sdk/tests/ ext/opentelemetry-ext-http-requests/src/ ext/opentelemetry-ext-http-requests/tests/ ext/opentelemetry-ext-wsgi/tests/
   flake8 opentelemetry-api/src/ opentelemetry-api/tests/ opentelemetry-sdk/src/ opentelemetry-sdk/tests/ ext/opentelemetry-ext-wsgi/src/ ext/opentelemetry-ext-wsgi/tests/ ext/opentelemetry-ext-http-requests/src/
   isort --check-only --recursive opentelemetry-api/src opentelemetry-sdk/src ext/opentelemetry-ext-wsgi/src ext/opentelemetry-ext-wsgi/tests ext/opentelemetry-ext-http-requests/src/