[devops] TravisCI tests fail more often than not - Need to simplify testing and mock network requests

Dear ml5 community,

I'm submitting a new issue. Please see the details below.

→ Step 1: Describe the issue 📝

Did you find a bug? Want to suggest an idea for feature?

• Want to suggest an idea

Currently the TravisCI tests fail more often than they pass. This has more to do with the fetching of images for analysis, the instantiation of models making big requests to external pretrained models from google or github servers, etc.

It would be wonderful if we can get this under control so that we can also start making a comprehensive set of tests for our features.