Include fits version dependency in README

[tampakis]

Currently 0.6.2

Some pertinent info for fits is in the hydra-derivatives readme

[grosscol]

Currently hydra-derivatives requires fits 0.6.2. The characterization included here was built against output from fits.sh 0.8.4, but it worked reasonably well for 0.6.2 output. The tests now check that they work for some 0.6.2 output.

[jcoyne]

How is hydra-derivatives requiring fits 0.6.2? Do you mean, it states 0.6.2 in its readme?

[grosscol]

Yes. Require was probably the wrong word for that. It states it as a dependency in the readme.