Fix build_docs test

[rwedge]

Pull Request Description

Resolves #802

Importing featuretools.autonormalize fails seemingly due to pip not installing a version of python-dateutil that satisfies both pandas and botocore.
Once boto/botocore#1872 is resolved we can remove the requirement

We could add more automated tests checking that featuretools.autonormalize and other entrypoint imports work, but I think it would be better to test those on the original library's repo instead of ours.

I'm thinking a test scheme like this:

• Featuretools library tests that featuretools[complete] install the additional library
• The additional library tests the ability to use the entry point each time Featuretools master branch is updated

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After creating the pull request: in order to pass the changelog_updated check you will need to update the "Future Release" section of docs/source/changelog.rst to include this pull request.