Updated CONTRIBUTING.md with dev env information

Author: hlovdal

CONTRIBUTING.md

@@ -12,7 +12,23 @@ Pull requests will trigger a Travis CI job.  The following two commands will be
  * `rubocop -D` - code style tests
  * `rspec` - functional tests
 
+ If you do not already have a working ruby development environment set up, run the following commands:
+
+```shell
+apt-get install ruby ruby-dev    # For Debian/Ubuntu
+dnf install ruby ruby-devel      # For Fedora
+yum install ruby ruby-devel      # For Centos/RHEL
+gem install bundler              # See note below about version
+gem install rubocop
+gem install rspec
+```
+
+As of writing this you want install a version 1 of bundler, `gem install bundler -v '1.17.3'`,
+since there is some incompability with regards to the
+[latest version 2 release of bundler](https://bundler.io/blog/2019/01/04/an-update-on-the-bundler-2-release.html)
+
 Be prepared to write tests to accompany any code you would like to see merged.
+See `SampleProjects/TestSomething/test/*.cpp` for the existing tests (run by rspec).
 
 
 ## Packaging the Gem