Document interface

[moustachio-belvedere]

As Ale mentioned in RHEOSafm issue JuliaRheology/RHEOSafm.jl#2, the RHEOS interface for contact models needs to be documented (and maybe tests added?)

I think once this is done, along with issue #93 we should probably consider releasing version 0.9.4?

[akabla]

Yes, a new release would be good so that the new doc is made available soon.

[akabla]

@Ab2425
While working on the doc for this section, I realise that the AFM interface is not named properly. I think we should call it "Hertz" as it is more about the Hertz contact model, rather than about the instrument used. If we don't change it soon, we'll get stuck once we add more contact models later. What do you think?

Ale, I think this would break the link with RHEOSafm, so we need a synchronize update if we go this way.

[akabla]

Good progress here, tests added, importcsv improved to match the usage of the new version #115
Documentation needs more examples, so moved to milestone 0.9.5.