Add jemalloc package

packages/jemalloc.rb

+require 'package'
+
+class Jemalloc < Package
+  description 'jemalloc is a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support.'
+  homepage 'http://jemalloc.net/'
+  version '5.0.1'
+  source_url 'https://github.com/jemalloc/jemalloc/releases/download/5.0.1/jemalloc-5.0.1.tar.bz2'
+  source_sha256 '4814781d395b0ef093b21a08e8e6e0bd3dab8762f9935bbfb71679b0dea7c3e9'
+
+  depends_on 'autoconf'
+  depends_on 'gawk'
+  depends_on 'libxslt'
+
+  def self.build
+    system './configure'
+    system 'make'
+  end
+
+  def self.install
+    system "make", "DESTDIR=#{CREW_DEST_DIR}", "install"
+  end
+end