drop 3.5 support

.github/workflows/testing.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}

setup.py

@@ -31,7 +31,6 @@ setup(
     python_requires=REQUIRES_PYTHON,
     classifiers=[
             'Development Status :: 5 - Production/Stable',
-            'Programming Language :: Python :: 3.5',
             'Programming Language :: Python :: 3.6',
             'Programming Language :: Python :: 3.7',
             'Programming Language :: Python :: 3.8',