Corrected OAuth scopes required.

I thought requiring a "user" OAuth scope for reading team membership was a bit odd, so I tried it with "read:org" and it worked, so correcting the documentation. "write:org" and "admin:org" are untested, but would make more sense than "user".
Edited out untested OAuth scope requirements.
Fixed bad grammar.
Merge pull request #465 from WrinklyNinja/master

Corrected OAuth scopes required.