README.md: protect emphasis before right single quote

redcarpet in rdiscount mode (RedcarpetCompat) renders

    *foo*’s

literally instead of providing emphasis.

If I write the right single quote as an entity:

    *foo*&#rsquo;s

then rdiscount, redcarpet and RedcarpetCompat all render the
emphasis.

This problem did show up in GitHub’s rendering of README.md.

Thanks to Trevor for pointing out redcarpet and RedcarpetCompat:

    #2 (comment)

README.md

@@ -177,7 +177,7 @@ cetera. This would require the user to remember to use the wrapper
 it fail then re-run it under the wrapper).
 
 A more automated solution that probably covers most of the problem
-scenarios for most users would be to set *tmux*’s `default-command`
+scenarios for most users would be to set *tmux*’s `default-command`
 option so that new windows start shells via the wrapper by default.
 The major area this would not cover would be commands given directly
 to `new-session` and `new-window` (there are some other commands