Fix travis (#147)

Update .travis.yml

.travis.yml

@@ -8,18 +8,20 @@ python:
   - "3.7"
   - "3.8"
   - "3.9"
+  - "3.10-dev"
   - "pypy"
   - "pypy3"
 
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install:
     - pip install pip --upgrade
+    - pip install importlib_metadata --upgrade # fix for broken py3.7
     - pip install pytest --upgrade
     # - pip install pylint --upgrade
 
 # command to run tests, e.g. python setup.py test
 script:
-    - python setup.py sdist --format=zip
+    - python setup.py sdist --formats=zip
     - pip install dist/pynmea2*.zip
     - py.test
     # - pylint -E pynmea2 ## pylint is not backwards compatible with itself