Document correction - update ReactRouter3.md

[Carr1005]

First, thanks for building such a useful HOC! I know react-router-3 is quite aged and may rarely be used in the community today, but I believe there must still be some who would like to adopt this library to save their life like me. 🙌

The changes are the same as the commit message:

1. Correct the code logic in the example of userIsNotAuthenticated.
2. Align minor inconsistencies in code examples.

FYI: The doc on Gitbook needs updates too.

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Also here is a proposal, would like to hear how the author and maintainers of this repo think:
I think the name of property authenticatedSelector in connectedRouterRedirect could be changed to a more neutral one. At the beginning, I misunderstood that the usage of connectedRouterRedirect is only for redirecting not valid/logged-in users to the page for authentication, cuz authenticatedSelector makes me think that it implies a "valid" status. I guess the doc's small mistake corrected with this PR was likely caused by a moment of confusion on this too.

@mjrussell

[mjrussell]

Ah thanks, this is a good doc fix. Sorry its taken so long for me to reply. I agree the original name is a bit misleading, it probably should be called simply "shouldRedirectSelector" or something like that. I'm hesitant to make such a change because I'm not longer really actively maintaining this repo (#315) and would involve a lot of documentation updates & new major version.