Adding a little additional token-related flexibility

Alex,

Before you begin work trying to get the oauth2 functionality pulled into the popular harvest repository, I'd like to incorporate these changes into the code too. I made these changes because I won't be running the tool from the command line; rather, I'll be making calls from other scripts and passing in the location of the credentials (which, if it doesn't exist, should initiate the authorization workflow).

I'll be in touch over email to discuss more.

Thank you,
Jesse