Remove cerberus (#58)

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## Description
Removed Cerberus module

## Related Issue
#57 

## Motivation and Context
Cerberus is not in open source anymore, that is why it should be
removed.

## How Has This Been Tested?
Run all tests

## Screenshots (if appropriate):

## Types of changes
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the boxes that apply: -->
- [x] 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:
<!--- Go over all the following points, and put an `x` in all the boxes
that apply. -->
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here to help! -->
- [x] My code follows the code style of this project.
- [ ] My change requires a change to the documentation.
- [ ] I have updated the documentation accordingly.
- [x] I have read the **CONTRIBUTING** document.
- [ ] I have added tests to cover my changes.
- [ ] All new and existing tests passed.