Add alternative instructions for Homebrew users.

src/README.md

diff --git a/src/README.md b/src/README.md
index 80e8668..095fb21 100644
--- a/src/README.md
+++ b/src/README.md
@@ -129,6 +129,10 @@
 
     sudo /opt/local/bin/port install autoconf automake libtool
 
+Alternative for Homebrew users:
+
+    brew intall autoconf automake libtool
+
 Then follow the Unix instructions above.
 
 **Note for cross-compiling**