Add tre package

packages/tre.rb

+require 'package'
+
+class Tre < Package
+  description 'The approximate regex matching library and agrep command line tool.'
+  homepage 'https://github.com/laurikari/tre'
+  version '6fb720'
+  source_url 'https://github.com/laurikari/tre/archive/6fb7206b935b35814c5078c20046dbe065435363.tar.gz'
+  source_sha256 'd2810576685b10c6bf9270793550032bdada04afd963fa4670a08fdc57859bdd'
+
+  depends_on 'autoconf'
+  depends_on 'automake'
+  depends_on 'gettext'
+  depends_on 'libtool'
+
+  def self.build
+    system './utils/autogen.sh'
+    system './configure'
+    system 'make'
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end