Add gifgen package

packages/gifgen.rb

+require 'package'
+
+class Gifgen < Package
+  description 'Simple high quality GIF encoding'
+  homepage 'https://github.com/lukechilds/gifgen'
+  version '1.1.2'
+  source_url 'https://github.com/lukechilds/gifgen/archive/1.1.2.tar.gz'
+  source_sha256 '95f69c63158315ad869ff36611026cce1a7d03f8c84716b1c21a44e71e8d6aee'
+
+  depends_on 'ffmpeg'
+  depends_on 'help2man'
+
+  def self.install
+    system "help2man -N ./gifgen > gifgen.1"
+    system "mkdir -p #{CREW_DEST_DIR}/usr/local/bin"
+    system "mkdir -p #{CREW_DEST_DIR}/usr/local/man/man1"
+    system "cp gifgen #{CREW_DEST_DIR}/usr/local/bin"
+    system "cp gifgen.1 #{CREW_DEST_DIR}/usr/local/man/man1"
+  end
+end