Add support for Matlab .mat files

[wolfv]

We can use libmatio and base off of @massich s work of packaging it for conda.

[SylvainCorlay]

Huge 👍 on this.

[massich]

Cool!!

We just start working on shipping https://github.com/massich/matio-cmake through my conda channel until I get a better handle on this conda business. Right now I'm fighting the windows shipping.

matio-cmake builds libmatio properly, but the testsuit does not build properly in windows. See this massich/matio-cmake#2 and the associated issue in tbeu/matio#84

[tdegeus]

A naive question, but I thought that Matlab now uses HDF5?

[wolfv]

I don't know a great deal about the .mat specification, but I initially also thought it might just be a simple format. But then I looked at matio (https://github.com/tbeu/matio) and it seems to be a crazy mess :)
But it's true that they switched to HDF5 of some sort in the more recent version, which means that HDF5 needs to be linked into matio for full format support.