CONTRIBUTING.md in vcr-3.0.3

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+## Contributing
+
+Install [bundler](http://gembundler.com/) and use it to install all the development dependencies:
+
+```console
+gem install bundler
+bundle install
+```
+
+You should be able to run the tests now:
+
+```console
+bundle exec rake
+```
+
+VCR uses [RSpec](http://github.com/rspec/rspec) for unit tests.  The specs are written in a very "focused" style, where each spec is concerned only with exercising the object under test, using mocks as necessary.  You can run the specs using `rake spec`.
+
+[Cucumber](http://cukes.info/) is used for end-to-end full stack integration tests that also function as VCR's documentation.
+
+## Problems running bundle install?
+
+If you get an error while running `bundle install`, it may be one of the "extras" gems which are not required for development. Try installing it without these gems.
+
+```console
+bundle install --without extras
+```