Update travis for Rails 5.1 and Ruby 2.5

Author: cupakromer

.travis.yml

@@ -6,11 +6,14 @@ script: bin/rake
 rvm:
   - 2.3.3
   - 2.4.0
+  - 2.5.0
 env:
+  - RAILS_VERSION='~> 5.1.0'
   - RAILS_VERSION='~> 5.0.0'
   - RAILS_VERSION='~> 4.2.8'
   - RAILS_VERSION='4-2-stable'
   - RAILS_VERSION='5-0-stable'
+  - RAILS_VERSION='5-1-stable'
 matrix:
   include:
     - rvm: 2.2.3

Gemfile-rails-dependencies

@@ -24,5 +24,5 @@ if version && !version.empty?
 elsif RUBY_VERSION.to_f < 2.4
   gem "rails", "~> 4.2.0"
 else
-  gem "rails", "~> 5.0"
+  gem "rails", "~> 5.1"
 end