Add pyyaml to requirements.in

[blazewicz]

Description

This gives information to package managers like pip that PyYAML is a required dependency.

Related Issue

#420

Motivation and Context

Fixes #420

How Has This Been Tested?

I believe no testing is required here.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[ljvmiranda921]

Hey thanks for catching this! I'll try to merge within the week and make a new release that includes the same version!
In case you really need it right now, I suggest doing a git clone first, updating the file manually, and running python setup.py install
Will do my best to merge within the week! 👍

[ljvmiranda921]

@all-contributors please add @blazewicz for bugfixes

[allcontributors]

@ljvmiranda921

I couldn't determine any contributions to add, did you specify any contributions?
Please make sure to use valid contribution names.

[ljvmiranda921]

@all-contributors please add @blazewicz for bug

[allcontributors]

@ljvmiranda921

I've put up a pull request to add @blazewicz! 🎉