Add documentation on SPARTAN dependencies

[harrisonCassar]

When adding the master README in #32, I left many sections undone with TODOs. When trying to build SPARTAN on a new device, there's a few dependencies I needed to get the build running. Let's add some documentation on these to the master README (listing them, and giving a small description), as well as in a separate markdown document (describing a "tutorial" of steps for how to install each and every single dependency) placed in the docs subdirectory.

For now, we'll have this document cover a Windows 10 computer using Ubuntu and a MacOS system, as most development is being done on these two systems.

A few things I found when installing the dependencies myself on a Windows 10 computer using Ubuntu:

• https://askubuntu.com/questions/355565/how-do-i-install-the-latest-version-of-cmake-from-the-command-line
• https://cmake.org/download/