bump google-api-python-client version to the latest

There was a recent release 1.12.0 which broke because of its dependency with `six`,
and there has been another patch update `1.12.1` which fixes that. I could have just forbidden
`1.12.0`, but didn't trust other versions and tried to just use the latest version.

Author: skshetry

setup.py

@@ -26,7 +26,8 @@
     description="Google Drive API made easy. Maintained fork of PyDrive.",
     long_description=open("README.rst").read(),
     install_requires=[
-        "google-api-python-client >= 1.7.12",
+        "google-api-python-client >= 1.12.1",
+        "six >= 1.13.0",
         "oauth2client >= 4.0.0",
         "PyYAML >= 3.0",
         "pyOpenSSL >= 19.1.0",