Add contributing language (#52)

Author: pcothenet

README.md

@@ -215,7 +215,13 @@ page = 1 # Pass in which page of preferences you'd like
 Patch::Preference.retrieve_preferences(page: page)
 ```
 
-## Development
+## Contributing
+
+While we value open-source contributions to this SDK, the core of this library is generated programmatically. Complex additions made directly to the library would have to be moved over to our generation code, otherwise they would be overwritten upon the next generated release. Feel free to open a PR as a proof of concept, but know that we will not be able to merge it as-is. We suggest opening an issue first to discuss with us!
+
+On the other hand, contributions to the README, as well as new test cases are always very welcome!
+
+### Testing locally
 
 To build the gem locally, run:
 
@@ -229,20 +235,16 @@ This will create a .gem file. To install the local gem:
 gem install patch_ruby-1.x.x.gem
 ```
 
-Install dependencies:
-
-```bash
-bundle install
-```
+### Running tests
 
-Set up required environment variables:
+Set up the required environment variable.
 
 ```bash
 export SANDBOX_API_KEY=<SANDBOX API KEY>
 ```
 
-Run tests:
+then run the tests:
 
 ```bash
-bundle exec rspec
+make test
 ```