add license to gemspec (and consequently the gem)

rspec.gemspec

@@ -7,16 +7,17 @@ Gem::Specification.new do |s|
   s.name        = "rspec"
   s.version     = RSpec::Version::STRING
   s.platform    = Gem::Platform::RUBY
+  s.license     = "MIT"
   s.authors     = ["Steven Baker", "David Chelimsky"]
   s.email       = "rspec-users@rubyforge.org"
   s.homepage    = "http://github.com/rspec"
   s.summary     = "rspec-#{RSpec::Version::STRING}"
   s.description = "BDD for Ruby"
 
-  s.rubygems_version   = "1.3.7"
   s.rubyforge_project  = "rspec"
 
-  s.files            = `git ls-files`.split("\n")
+  s.files            = `git ls-files -- lib/*`.split("\n")
+  s.files           += ["License.txt"]
   s.test_files       = `git ls-files -- {spec,features}/*`.split("\n")
   s.executables      = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.extra_rdoc_files = [ "README.markdown" ]