Missing documentation for local execution of pytest/tox

[srenfo]

There is no explicit documentation on how to run the test suite.

As for requirements, at the very least ipmitool needs to be installed on Debian/derivatives, in addition to the other requirements. Currently, that fact is only implicitly documented in travis.yml and Dockerfile. ipmitool is not required at runtime and is therefore (appropriately?) missing from install.rst. Also, tox should be mentioned somewhere, since right now only the existence of tox.ini tips you off that that's how the tests are run.

Suggestions:

1. add a subsection to the install documentation since that's where the other requirements are documented
2. add a small section to the top-level README.md
3. roll it into a CONTRIBUTING.md (since that's where development-oriented documentation could live)

I can try my hand at a PR. I would lean towards adding it to the README.

[glaslos]

How about extending https://conpot.readthedocs.io/en/latest/development/guidelines.html ? Maybe add more deep links to the README?