Remove uses of x.0 or x. used to force float division

There are a number of places in chaco where we seem to have used `integer.0` or `integer.` e.g. `1.0` or `1.` to force float division. This might have been necessary in Python 2 but is no longer necessary in Python 3. We should be able to remove most of these `integer.0` uses in the codebase.

This is not worth doing unless it can be done with a simple search and replace, possibly using a regex.