Update rake

Author: andrew

split-api.gemspec

@@ -22,5 +22,5 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'bundler',     '~> 1.0'
   gem.add_development_dependency 'rspec',       '~> 2.6.0'
   gem.add_development_dependency 'rack-test',   '~> 0.6'
-  gem.add_development_dependency 'rake',        '~> 10.0'
+  gem.add_development_dependency 'rake',        '~> 12.0'
 end