Add 'developer tools' page to technical wiki

[tkimia]

This a is a part of a bigger effort to add answers to common questions people have when joining the project.

Detailed Description

One of the pages will be about developer tools, which will include the gems we use and why we use them.
These include:

• IDEs and Debugging
• Testing with Minitest and FactoryBot
• RVM

Please comment with any tools you want to see documented