Add rack package

Need to go get before go build

Add bash command completion support

packages/rack.rb

+require 'package'
+
+class Rack < Package
+  description 'The Rackspace Command Line Interface (rack CLI) is a unified tool for managing your Rackspace services.'
+  homepage 'https://github.com/rackspace/rack'
+  version '1.2'
+  source_url 'https://raw.githubusercontent.com/rackspace/rack/1.2/README.md'
+  source_sha256 '2681ad55f204718cb8bcc8cbe0b2da66897f3310cb78576ae248a252a9b7f544'
+
+  binary_url ({
+  })
+  binary_sha256 ({
+  })
+
+  depends_on 'go' => :build
+
+  def self.install
+    system "go get github.com/rackspace/rack"
+    system "cd ~/go/src/github.com/rackspace/rack && git checkout 1.2"
+    system "install -Dm644 ~/go/src/github.com/rackspace/rack/setup/commandcompletion_bash.sh #{CREW_DEST_PREFIX}/share/rack/commandcompletion_bash.sh"
+    system "go build -o #{CREW_DEST_PREFIX}/bin/rack github.com/rackspace/rack"
+  end
+
+  def self.postinstall
+    puts
+    puts "To add command completion in bash, execute the following:".lightblue
+    puts "echo 'if [ -f #{CREW_PREFIX}/share/rack/commandcompletion_bash.sh ]; then' >> ~/.bashrc".lightblue
+    puts "echo '  source #{CREW_PREFIX}/share/rack/commandcompletion_bash.sh' >> ~/.bashrc".lightblue
+    puts "echo 'fi' >> ~/.bashrc".lightblue
+    puts "source ~/.bashrc".lightblue
+    puts
+  end
+end