Add Rails 5.0 and 5.1 to the Appraisals list.

Appraisals

@@ -1,7 +1,15 @@
 appraise "rails-4.1" do
   gem "rails", "~> 4.1.0"
-end
+end if RUBY_VERSION.to_f < 2.4
 
 appraise "rails-4.2" do
   gem "rails", "~> 4.2.0"
 end
+
+appraise "rails-5.0" do
+  gem "rails", "~> 5.0.0"
+end
+
+appraise "rails-5.1" do
+  gem "rails", "~> 5.1.0"
+end

vault.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*", "LICENSE", "Rakefile", "README.md"]
   s.test_files = Dir["spec/**/*"]
 
-  s.add_dependency "rails", [">= 4.1", "< 5.1"]
+  s.add_dependency "rails", [">= 4.1"]
   s.add_dependency "vault", "~> 0.5"
 
   s.add_development_dependency "appraisal", "~> 2.1"