Tried adding vectorspace support to invertible.

This would put the 'Monoidal'-option-invertible to use; unfortunately it turns out it's basically just wrong this way.
Added 'fzip' function.

This is a natural analogy to 'zip' as compared to 'zipWith' / 'fzipWith', albeit not all that useful since only the target category can be set from the outside anymore, which is often hampered when a 'function' morphism is immediately applied to a value with '$'.
Added basic example of vector space category.