Update Python requirement to 3.7

Author: lesamouraipourpre

setup.py

@@ -13,7 +13,7 @@
                 'circuitpython_build_tools.scripts'],
       package_data={'circuitpython_build_tools': ['data/mpy-cross-*']},
       zip_safe=False,
-      python_requires='>=3.4',
+      python_requires='>=3.7',
       install_requires=['Click', 'requests', 'semver'],
       entry_points='''
         [console_scripts]