Add tree (1.7.0) package

Tree is a recursive directory listing command that produces a depth indented listing of files.

Tested as working properly on Samsung XE50013-K01US.

packages/tree.rb

+require 'package'
+
+class Tree < Package
+  version '1.7.0'
+  source_url 'http://mama.indstate.edu/users/ice/tree/src/tree-1.7.0.tgz'
+  source_sha1 '35bd212606e6c5d60f4d5062f4a59bb7b7b25949'
+
+  def self.build
+    system "sed -i 's,/usr,/usr/local,g' Makefile"
+    system "make"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end