Update mws.py
Update mws.py

get_matching_product_for_id acts like get_matching_product.
changed id to "ids" since in other function there is asins, skus ...

Updated docs with proper case for the possible identifier values and added a hint that this needs to be in the correct case.
GriceTurrble/python-amazon-mws,BigFlySports/python-amazon-mws,hairyjerry/python-amazon-mws,bloodywing/python-amazon-mws,jameshiew/mws,bpipat/mws,juokaz/python-mws-sdk,ziplokk1/python-amazon-mws,Bobspadger/python-amazon-mws,czpython/python-amazon-mws