Optional packages #14

Look into building optional packages which are optimized for specific packages. If I'm not mistaken, if mypyc is compiled with for example torch it is able to improve performance a bit more than it currently is. We could release different wheels for these, installed through pip install decent-array[torch], pip install decent-array[tf] etc. We could also have combinations of packages but I don't really see the reason for this, maybe an [all] but its not really recommended to combine some of the accelerator packages