wireshark: update caveat with OS X workaround

Formula/wireshark.rb

@@ -25,5 +25,23 @@ class Wireshark < Formula
     ENV.j1 # Install failed otherwise.
     system "make install"
   end
+
+  def caveats; <<-EOS.undent
+      If your list of available capture interfaces is empty
+      (default OS X behavior), try the following commands:
+
+        wget https://bugs.wireshark.org/bugzilla/attachment.cgi?id=3373 -O ChmodBPF.tar.gz
+        tar zxvf ChmodBPF.tar.gz
+        open ChmodBPF/Install\\ ChmodBPF.app
+
+      This adds a launch daemon that changes the permissions of your BPF
+      devices so that all users in the 'admin' group - all users with
+      'Allow user to administer this computer' turned on - have both read
+      and write access to those devices.
+
+      See bug report:
+        https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=3760
+    EOS
+  end
 end