add install instructions for osx

There are other ways to do this, but this seems to be the most commonly
used and easiest way to get the job done. Alternate methods could be
added but at least having this one will alert folks that using this on
OSX is an option.

README.md

@@ -293,6 +293,13 @@ Or you can do it yourself manually using the documentation on installing AUR pac
 If you prefer to use the devel package that installs the git HEAD version it
 is available [here](https://aur.archlinux.org/packages/vcsh-git/).
 
+#### Mac OSX
+
+Formulas are available for vcsh as well as git and myrepos through [homebrew](http://brew.sh). The
+vcsh formula is set to depend on myrepos, so you only need one install command:
+
+    brew install vcsh
+
 #### From source
 
 To install the latest version from git: