Changed E*Trade Methods

E*Trade supports software (with Verisign). I also updated the docs to show both methods.
Remove eBay SMS

As per an email I received from Michael Kidd. He contacted support and confirmed SMS 2FA isn't available for eBay.
Add section on site criteria, closes #394
Add contributing markdown file
Move Contributing section to CONTRIB.md
Merge pull request #447 from jamcat22/patch-1

Changed E*Trade Methods
heroku 2fa is in beta.
Merge pull request #453 from rajiv/heroku

heroku 2fa is in beta.