Document and inform about storage classes

[rodet]

I used this project for a website and observed that the website was very slow, although everything looked fine. After a couple weeks of tests, I found out this was because I was using the Bronze storage class for volumes.

I understand the description should stay vendor neutral, so this project could document the requirements in terms of IOPS. In my case, 10 IOPS/GB gave a satisfying result for a small sized WordPress instance.