Add explicit configuration path for ReadtheDocs

[mrmundt]

Fixes #1551

Summary/Motivation:

RTD now requires an explicit path to the conf.py file

Changes proposed in this PR:

• Add explicit path

Legal Acknowledgement

By contributing to this software project, I agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the license terms described in the LICENSE.txt file at the top level of this directory.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[ksbeattie]

Beautiful!