Add license to gemspec

resqutils.gemspec

@@ -8,6 +8,7 @@ Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
   s.authors     = ['Stitch Fix Engineering']
   s.email       = ['[email protected]']
+  s.license     = "Apache License Version 2.0, January 2004"
   s.homepage    = "https://github.com/stitchfix/resqutils"
   s.summary     = "Utilities for using Resque in a Rails app"
   s.description = "Utilities for using Resque in a Rails app"