Add Python POST examples

[robertdenton]

Hi MailChimp friends,

Just got done creating some scripts to send daily newsletters and circled back around to make some super simple POST request examples that would have helped me out when I was first getting started with your API. This could also help close out #21 but I'll leave that up to you.

I focused on creating a campaign and sending a test email because those were two basic functions I used a lot during testing and neither can create big problems (like accidentally sending a campaign to a major list).

Also added a requirements.txt, which isn't really needed but could be good for more complex examples in the future.

Thanks for this repo, it's very helpful.

Edit: Please disregard the inordinate amount of commits below. I originally was using this fork for development of new scripts to send daily newsletters but I stripped those out into a new private repo.

[deezone]

I encourage you to change the title of the PR to make reference to Python.

[robertdenton]

@DeeZone Thanks, added Python to PR title.