Update to Python 3.7 for futures

.github/workflows/build.yml

@@ -14,10 +14,10 @@ jobs:
       id: repo-name
       run: |
         echo ::set-output name=repo-name::adafruit-extended-bus
-    - name: Set up Python 3.6
+    - name: Set up Python 3.7
       uses: actions/setup-python@v1
       with:
-        python-version: 3.6
+        python-version: 3.7
     - name: Versions
       run: |
         python3 --version

setup.py

@@ -44,6 +44,7 @@ setup(
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
+        "Programming Language :: Python :: 3.7",
     ],
     # What does your project relate to?
     keywords="adafruit blinka circuitpython micropython extended_bus busio i2c spi extended "