Remove unused dependencies. Rails generator should be extracted to it…

… own gem.

mangopay.gemspec

@@ -1,4 +1,4 @@
-$:.unshift(File.join(File.dirname(__FILE__), 'lib'))
+$LOAD_PATH.unshift(File.join(File.dirname(__FILE__), 'lib'))
 
 require 'mangopay/version'
 
@@ -20,11 +20,8 @@ Gem::Specification.new do |s|
 
   s.add_dependency('multi_json', '>= 1.7.7')
 
-  s.add_development_dependency('rake', '~> 10.1.0')
-  s.add_development_dependency('rspec', '~> 2.14.1')
-  s.add_development_dependency('capybara', '~> 2.1.0')
-  s.add_development_dependency('capybara-webkit', '~> 1.0.0')
-  s.add_development_dependency('rails', '~> 4.0.0')
+  s.add_development_dependency('rake', '>= 10.1.0')
+  s.add_development_dependency('rspec', '>= 3.0.0.rc1')
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- spec/*`.split("\n")