Update Product

We may need a fix later because the "change-asset" endpoint from the MM API is not working yet, so no real tests have been done.

Commit 1: Add method "Asset.update_product"

Change tariffs and add one shot additional_bonds of a given asset using this PATCH
method

Add 'TariffChangeRequiredParamsError'

Throw an error if an asset product update is done without all the required
parameters.

Commit 3: Update CHANGELOG