Remove Bundler version dependency

Author: haruyama-makoto

.travis.yml

@@ -8,7 +8,6 @@ rvm:
   - 2.2
 
 before_install:
-  - gem uninstall bundler -x
   - gem install bundler -v 1.14.3
 
 before_script:

zstd-ruby.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
   spec.extensions    = ["ext/zstdruby/extconf.rb"]
 
-  spec.add_development_dependency "bundler", "~> 1.14"
+  spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rake-compiler", '~> 1'
   spec.add_development_dependency "rspec", "~> 3.0"