Changed all the examples with ugly platform-dependent float output to use

Changed all the examples with ugly platform-dependent float output to use
numbers that display nicely after repr().  From much doctest experience
with the same trick, I believe people find examples with simple fractions
easier to understand too:  they can usually check the results in their
head, and so feel confident about what they're seeing.  Not even I get a
warm feeling from a result that looks like 70330.345024097141 ...