New: Add no-extra-bind rule to flag unnecessary bind calls (fixes #982)

Fixes #982

This is my first pr here, if I'm doing something wrong, please tell me, and I'll rebase.
Before merge, [cli-engine.js](https://github.com/eslint/eslint/blob/master/lib/cli-engine.js#L175) should be fixed, it violates this new rule.
Please add JSDoc comments for helper functions. Also, this should be `getTopScope()` to indicate a value is being retrieved.