Operators on weights

`+`	[add](weight.add.ipynb)	Sum
`*`	[multiply](weight.multiply.ipynb)	Product
`**`	[multiply](weight.multiply.ipynb)	Repeated multiplication
`/`	[ldivide](weight.ldivide.ipynb)	Left quotient
`//`	[rdivide](weight.rdivide.ipynb)	Right quotient