Use stable units for FIO

[kdvalin]

Currently this wrapper puts whatever FIO spits out as MB/s or IOPs. The normal output scales units to make it more readable. When blindly converting to a CSV, this can cause problems when comparing multiple systems to each other.

This can be done in a few different ways.

#21 introduces a JSON file, which has stable units.

We can also try converting the units to an agreed-upon unit

[malucius-rh]

I have a fix almost ready for this, which does the jsonificiation and deals with the units issue.