Remove the version constraint of bundler

Author: mrkn

pycall.gemspec

@@ -36,7 +36,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
   spec.extensions    = ["ext/pycall/extconf.rb"]
 
-  spec.add_development_dependency "bundler", ">= 1.17.2"
+  spec.add_development_dependency "bundler"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rake-compiler"
   spec.add_development_dependency "rake-compiler-dock"