Improving dockerfile and removing pipenv

[timogoosen]

What this does?

• Improving dockerfile
• Removing pipenv and replacing with plain pip.

This will speed up builds big time. Pipenv can be a big pain to deal with sometimes. Better to stick to plain pip sometimes to avoid headaches down the line.

Upcoming changes:

In a next PR i'll make a change that allows you to build the code faster, like where it won't reinstall everything if you rerun the docker build after only changing the code. Then it will just copy in the new code into the container.

[drewbitt]

An even larger speedup is to remove Google Chrome & selenium for an external dockerized browserless/chrome or playwright-chrome which should be added as an environment variable URL. That dependency is too huge to install in this container itself. That said, this is working for me and fixes #57. It should be merged.