Add openblas package. (#2192)

* Add openblas package.

* Fix openblas package.

packages/openblas.rb

+require 'package'
+
+class Openblas < Package
+  description 'OpenBLAS is an optimized BLAS library'
+  homepage 'http://www.openblas.net/'
+  version '0.2.20'
+
+  source_url 'https://github.com/xianyi/OpenBLAS/archive/v0.2.20.zip'
+
+  source_sha256 'bb5499049cf60b07274740a4ddd756daa0fe2c817d981d7fe7e5898dcf411fdc'
+
+  depends_on 'unzip' => :build
+
+  def self.build
+    system "make"
+  end
+
+  def self.install
+    system "make",
+           "DESTDIR=#{CREW_DEST_DIR}",
+           "PREFIX=#{CREW_PREFIX}",
+           "LIBDIR=#{CREW_LIB_PREFIX}",
+           "install"
+  end
+end