Add fetch package

packages/fetch.rb

+require 'package'
+
+class Fetch < Package
+  description 'fetch makes it easy to download files, folders, or release assets from a specific commit, branch, or tag of a public or private GitHub repo.'
+  homepage 'https://github.com/gruntwork-io/fetch'
+  version '0.1.1'
+  source_url 'https://github.com/gruntwork-io/fetch/archive/v0.1.1.tar.gz'
+  source_sha256 'ff3072da89c36a5031a3585ec6898113005185e76f626cf4ca8cffee4b62446d'
+
+  depends_on 'go'
+
+  def self.build
+    system "go get github.com/urfave/cli"
+    system "go get github.com/hashicorp/go-version"
+    system "sed -i 's,codegangsta,urfave,g' main.go"
+  end
+
+  def self.install
+    system "mkdir -p #{CREW_DEST_DIR}/usr/local/bin"
+    system "go build -ldflags \"-X main.VERSION=v0.1.1\" -o #{CREW_DEST_DIR}/usr/local/bin/fetch"
+  end
+end