Fix pip installation when wheel is not installed

[edumco]

Installation error when wheel is not installed

Scenario

Pre condition

• wheel is not installed

Steps

• Navigate to the source code root

• Install pyan3 from code using pip:

    pip install .

Fix

• I've added the wheel package to the setup stage on setup.py so it will only be installed if the user wanted to install from code.

[Technologicat]

I suppose this is ok. Thanks!

[Technologicat]

@edumco : You've posted quite a few accepted PRs to pyan already, so I've invited you as a collaborator to this repository.