Add xe (0.6.1) package

xe is a new tool for constructing command lines from file listings or
arguments, which includes the best features of xargs(1) and apply(1).

Tested on Samsung XE50013-K01US (x86_64).

packages/xe.rb

+require 'package'
+
+class Xe < Package
+  version '0.6.1'
+  source_url 'https://github.com/chneukirchen/xe/archive/v0.6.1.tar.gz'
+  source_sha1 '76c0a31c4d646314c3e92753a2fec3ae7cedad1d'
+
+  def self.build
+    system "make", "PREFIX=/usr/local"
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install" 
+  end
+end