Function to reset GA credentials on pandas.io.ga
It's pretty easy to authenticate yourself with the wrong credentials for GA - lots of us have different accounts and id's.  In the pandas utility, if you get yourself authenticated, but then replace your secrets file with another one, you will keep getting a 401 error forever after saying your credentials are messed up. The fix is apparently to delete the analytics.dat file in the pandas.io directory so you can use your new client secrets.json file. A function to do this might be nicer (and require less hunting).

Chang asked me to file this.
