diff: allow tolerance only between floats

[dbrakman]

Description

For #181

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[joesolly]

Instead of this change, why don't we set the default tolerance to 1e-int_Max?

[dbrakman]

There is no int_Max: https://docs.python.org/3/whatsnew/3.0.html#integers

Applying any tolerance for integers would impose a guess as to what magnitudes of numbers people are likely to use or what range of values one's test suite can accept. The tolerance parameter's stated goal of allowing floating point imprecision isn't applicable to integers