Revert "zinc"

This reverts commit 584da8f06db9d7ba3db48ae6603c40a250a065c7, reversing
changes made to 0036b32206b0cbdb3dd5ee6df973e7175d0fc87c.
Merge branch 'master' of https://github.com/streppneumo/isp

Conflicts:
	model/metabolism/transport/Zinc_Manganese_ABC.py