Making a pull request

Step-by-step

Does your bug fix or feature have a corresponding GitHub issue? If not, open one!
Create a new issue branch using the following naming convention:
```
git checkout -b issue_1234_short_description_of_issue
```
Add your changes and commit them to your issue branch.
- If it's a bug fix add a test
- If it's a new feature, document it and add tests!
When you're ready, push your local branch to your fork
```
git push origin issue_1234_short_description_of_issue
```
- In order to enable the automatic integration tests directly on your fork, simply register on Travis and add your repository
Create a pull request on GitHub from the branch in your fork to the correct branch of aiidateam/aiida_core
- Open your pull request only once you believe your changes are ready to be merged.
  If you keep pushing changes to an open PR, developers are flooded with emails.
- Use the PR title to describe its contents (bad: "Fix issue 1234", good: "quicksetup now works without sudo")
- Mention the issue number in the description of the PR
If any of the automatic integration tests fail, fix them until you get the green check mark.
The aiida-core maintainers will now start reviewing your PR.

All PRs undergo continuous integration testing using Travis. In order to pass, your PR needs to:

pass the pre-commit checks, including coding style and static analysis
pass all aiida tests
- using the django and sqlalchemy database backends
- on python2.7 and python3.6
build the documentation without warnings

On top of this, developers may ask you to document and test added functionality.