chore(package): adding contributing.md

Author: gergelyke

CONTRIBUTING.md

@@ -0,0 +1,14 @@
+## Guidelines for contributing to trace-nodejs
+
+RisingStack welcomes contributions for the trace-nodejs module by anyone who'd like to make it better!
+
+To make everyone's life easier, we have a few guidelines on how you can do that.
+
+##### Tech
+
+* Make sure to have tests for all your changes
+* Code has to run on 0.10+ for backwards compatibility
+
+##### Legal
+
+By sending pull request you agree to grant RisingStack, Inc. perpetual, irrevocable, non-exclusive, worldwide, no-charge, royalty-free, unrestricted license in the code, algorithms, idea, object code, patch, tool, sample, graphic, specification, manual or documentation (“Your Contribution”) to reproduce, publicly display, publicly perform, sublicense, and distribute Your Contribution and such derivative works. You provide your contributions on an "as is" basis, without warranties of any kind, including warranties of correctness or fitness for a particular purpose.