Add a better way to define text-object

Originally reported by: **Yufan Lou (Bitbucket: [louy2](https://bitbucket.org/louy2), GitHub: [louy2](https://github.com/louy2))**

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A function which wraps matching and binding:
http://stackoverflow.com/a/22418983/2449800

I have been using this function myself and think it is good enough to be default.

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- Bitbucket: https://bitbucket.org/lyro/evil/issue/455

Review the linked Stack Overflow function and compare it with how text objects are currently defined in the repository. Determine the intended default behavior and identify the relevant implementation and test entry points before proposing a scoped change; done means the new definition method is documented by tests and works for matching and binding.

Written by the indexing model from the issue text.