Depend on RSpec-expectations, not RSpec

It's more precise requirement.  Development dependency on RSpec moved to
Gemfile.

Author: skalee

Gemfile

@@ -4,5 +4,6 @@ gemspec
 
 group :test do
   gem "cucumber", "~> 1.1", ">= 1.1.1"
+  gem "rspec", "~> 2.0"
   gem "rake", "~> 10.0"
 end

json_spec.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |gem|
   gem.license     = "MIT"
 
   gem.add_dependency "multi_json", "~> 1.0"
-  gem.add_dependency "rspec", "~> 2.0"
+  gem.add_dependency "rspec-expectations", "~> 2.0"
 
   gem.add_development_dependency "bundler", "~> 1.0"