LICENSE was introduced in EUMM 6.30_01

According to the ExtUtils::MakeMaker changelog, support for the
LICENSE field was introduced in 6.30_01, but Dancer was only
adding this field for versions 6.30_02 and above.
scripts/dancer: Convert version to float

ExtUtils::MakeMaker usually has a $VERISON like '6.30_02', and
trying to numerical comparisons on that will yield something like

 Argument "6.30_02" isn't numeric in numeric ge (>=) at Makefile.PL line 5.

when trying to run the generated Makefile.PL.

This change does an ugly regexp, simply removing the underscore,
on the string prior to using it for comparison. I.e.:

 6.30_02 => 6.3002
amend Changelog
Merge branch 'pr/891' into devel