Add autossh package

packages/autossh.rb

+require 'package'
+
+class Autossh < Package
+  description 'The purpose of autossh is to start an SSH connection, monitor it, and restart it if necessary.'
+  homepage 'http://www.harding.motd.ca/autossh'
+  # No releases available so the only option is to use the master branch
+  version '9c72d3'
+  source_url 'https://github.com/jonhiggs/autossh/archive/9c72d3b6f77bfe2ad57844128ea46019fecb7fdb.tar.gz'
+  source_sha256 '39497e1ccd80f781282e8f6387bb3ae5b1501807a39aeced95e8be57c3778cba'
+
+  def self.build
+    system './configure'
+    system 'make'
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end