doc: adding minor clarification to CONTRIBUTING.MD (#79)

Thanks for contributing!

CONTRIBUTING.md

@@ -5,14 +5,13 @@
 Should you run into issues with the project, please don't hesitate to let us know by
 [filing an issue](https://github.com/axa-group/nlp.js/issues/new).
 
-Pull requests containing only failing tests demonstrating the issue are welcomed
-and this also helps ensure that your issue won't regress in the future once it's fixed.
+Pull requests containing only failing tests demonstrating an issue are also welcomed. Having these tests will help avoiding future regressions of this specific issue once it's fixed.
 
 ## Pull Requests
 
 We accept [pull requests](https://github.com/axa-group/nlp.js/pull/new/master)!
 
-Generally we like to see pull requests that
+Generally we like to see pull requests that:
 
 - Maintain the existing code style
 - Are focused on a single change (i.e. avoid large refactoring or style adjustments in untouched code if not the primary goal of the pull request)
@@ -32,4 +31,4 @@ From the root directory, run the tests.
 
 ```shell
 npm test
-```
+```