Floating point with zero digits after the comma

[tovrstra]

Probably related to #107 and #99.

The following works as expected:

In [0]: parse("foo_{:02d}t", "foo_20t")
Out[0]: <Result (20,) {}>

A very similar construct returns None, which means parse is not behaving as the inverse of format for this case:

In [1]: parse("foo_{:02.0f}t", "foo_20t")

(Sorry for the quick complaining comment. I'm in a hurry but wanted to let you know anyway. Thanks for the great library.)