First draft of contribution document

Author: metdinov

CONTRIBUTING.md

@@ -0,0 +1,67 @@
+Contributing
+============
+
+Contributions are welcome and very much appreciated. Credit will be appropriately given.
+
+## License
+
+By contributing, you agree that your contributions will be licensed under its MIT License.
+
+## Code contributions
+
+To begin contributing to the project, please follow these steps.
+
+1. [Fork](https://help.github.com/en/articles/fork-a-repo) the repo.
+2. Clone your fork locally:
+
+```shell
+$ git clone [email protected]:your_username/backtester_options.git
+```
+
+3. Create the environment and install dependencies:
+
+```shell
+$ make init
+```
+
+4. Create your development branch from `master`
+
+```shell
+$ git checkout -b your_branch master
+```
+
+5. Start coding your contribution (Thanks!)
+
+6. Make sure your code passes all tests, lints and is formatted correctly (`TODO`: Add linting, code formatting to Travis.)
+
+6. Submit a pull request with a brief explanation of your work.
+
+## Types of Contributions
+
+### Bug reports
+
+Make sure to follow the setup steps detailed in the [readme](README.md). If you find a bug, please create an issue with the label `bug` and provide the following information:
+
+- Operating System and version.
+- Steps taken to replicate the bug.
+- What was the expected output and what actually happend.
+- Any details of your local environment that might be helpful for troubleshooting.
+
+### Bug fixes
+
+If you find a bug issue you want to fix, follow the steps outlined [above](#code-contributions) and submit a pull request with a link to the original issue.
+
+### Proposing Features
+
+Create an issue detailing what functionality you'd like to see implemented. If you can, provide general advice as to how the proposed feature could be done.
+
+### Implementing Features
+
+Find an issue with the label `help wanted` or `improvement` and [start coding](#code-contributions).  
+When you are done, submit a pull request with a link to the original issue and some code samples showing how the code works. Tests are expected when adding new functionality.
+
+
+### Documentation
+
+We encourage users to improve our project documentation, either via docstrings, markdown documents to be added to the [project wiki](https://github.com/lambdaclass/backtester_options/wiki) or writing blog posts.  
+Let us know via issues labeled `docs` and we'll credit you appropriately.