mtr: add HEAD

Closes Homebrew/homebrew#21264.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/mtr.rb

@@ -6,8 +6,11 @@ class Mtr < Formula
   mirror 'ftp://ftp.bitwizard.nl/mtr/mtr-0.82.tar.gz'
   sha1 'f1319de27324d85898a9df0a293a438bbaaa12b5'
 
+  head 'https://github.com/traviscross/mtr.git'
+
   depends_on 'pkg-config' => :build
   depends_on 'gtk+' => :optional
+  depends_on :automake if build.head?
 
   def install
     # We need to add this because nameserver8_compat.h has been removed in Snow Leopard
@@ -17,6 +20,7 @@ class Mtr < Formula
       --prefix=#{prefix}
     ]
     args << "--without-gtk" if build.without? 'gtk+'
+    system "./bootstrap.sh" if build.head?
     system "./configure", *args
     system "make install"
   end