Removes bundler dependency as it is not needed

Since bundler should already be installed on the underlying system,
it only gets more complicated if it is part of the dependencies.

Author: sfroehler

shipcloud.gemspec

@@ -22,7 +22,6 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = ">= 2.0"
 
   spec.add_runtime_dependency "json", ">= 1.8.0"
-  spec.add_development_dependency "bundler", ">= 1.3.0", "< 2.0"
   spec.add_development_dependency "rake", "~> 12.0"
   spec.add_development_dependency "rspec", "~> 3.6"
   spec.add_development_dependency "webmock", "~> 3.0"