Cucumber expressions 600 match integers as floats

[aslakhellesoy]

Summary

Match 0 with a {float} parameter

Details

Change the float regexp to make the decimal part optional.

Motivation and Context

See #600.

How Has This Been Tested?

With new tests

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist:

• I've added tests for my code.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[luke-hill]

Not that important, but it'd be slightly smaller if we used -?\d*[.,]?\d+ - Ran it through a bunch of expressions online and it's the same.