Install Dependabot and configure related settings

[quantum9Innovation]

This issue is part of a series of tasks listed in #81.

[Quantalabs]

@quantum9Innovation will start on #80, and I'll start work on this issue

/claim

[Quantalabs]

Work has started on branch patch-81

[quantum9Innovation]

Use:

git branch -m patch-#81 patch-81
git fetch origin
git branch -u origin/patch-81 patch-81

to rename your local branch. Always use patch-{issue #} instead of patch-#{issue #} when creating branch names.

[quantum9Innovation]

The problem right now is that we need some way to configure Travis CI to run tests with the latest dependencies that we support. That way, when dependabot updates our dependencies, we can run checks to confirm that our package is compatible with those updates.

$ pip install -r requirements-dev.txt has already failed on Travis CI. This is because pip installs all the dependencies simultaneously. And since plotly, one of the dependencies, does not correctly list pandas as a sub-dependency, we must add pandas to the requirements-dev.txt file. However, when pip simultaneously installs all the dependencies, pandas is not installed before plotly and this raises an error.

At least that's what we know so far. @Quantalabs any ideas?