added gem task for easy local packaging

.gitignore

@@ -1,2 +1,3 @@
 .DS_Store
-html/*
+html/*
+pkg

Rakefile

@@ -1,7 +1,7 @@
 require 'rake'
 require "rake/rdoctask"
 require 'spec/rake/spectask'
-
+require 'rake/gempackagetask'
 
 spec = Gem::Specification.new do |s|
   s.name = "couchrest"
@@ -25,6 +25,8 @@ spec = Gem::Specification.new do |s|
   s.add_dependency("extlib", ">= 0.9.6")
 end
 
+::Rake::GemPackageTask.new(spec) { |p| p.gem_spec = spec }
+
 desc "Update Github Gemspec"
 task :gemspec do
   skip_fields = %w(new_platform original_platform)