Polling fallback message help

Motivated by: #284. [ci skip]
Perfecto! Sounds good. So, how's this for the README(?):

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> ### Getting the [polling fallback message](#options)?

> Please visit the [installation section of the Listen WIKI](https://github.com/guard/listen/wiki#installation) for more information and options for potential fixes.

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And then I can start organizing and adding to the Mac/Windows section of the WIKI based on all the things we've already discussed. :+1: