[travis fix] Move testing gems to Gemfile in test group

Author: waterlink

Gemfile

@@ -1,2 +1,10 @@
 source "https://rubygems.org"
+
 gemspec
+
+group :test do
+  gem "rspec"
+  gem "rack-test"
+  gem "webmock"
+end
+

rack-reverse-proxy.gemspec

@@ -9,10 +9,7 @@ Gem::Specification.new do |s|
   s.require_paths = ["lib"]
   s.summary       = 'A Simple Reverse Proxy for Rack'
 
-  s.add_development_dependency "rspec", "~> 3.1"
   s.add_development_dependency "rake", "~> 10.3"
-  s.add_development_dependency "rack-test", "~> 0.6"
-  s.add_development_dependency "webmock", "~> 1.18"
   s.add_development_dependency "guard-rspec"
   s.add_development_dependency "guard-bundler"