Fix links in contributing.md to use markdown format rather than github wiki format.

Author: myronmarston

Diff for: CONTRIBUTING.md

@@ -1,6 +1,6 @@
 ## Contributing
 
-Install [[bundler | http://gembundler.com/]] and use it to install all the development dependencies:
+Install [bundler](http://gembundler.com/) and use it to install all the development dependencies:
 
 ```console
 gem install bundler
@@ -26,9 +26,9 @@ You should be able to run the tests now:
 bundle exec rake
 ```
 
-VCR uses [[RSpec 2 | 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`.
+VCR uses [RSpec 2](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.
+[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?