Test with defined, not length, to avoid warnings.

@melmothX reported that this is spamming the logs with uninitialized variable
warnings.
changelog

Fixes #899
Merge branch 'pr/899' into devel
Fix bug (request->header inside routes of Dancer->dance($request) threw error exception)
Amend changelog
Merge branch 'pr/702' into devel
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
change JSON serializer to use JSON's "-support_by_pp" option to enable the "escape_slash" option. also fix Dancer::Serializer::JSON's handling of config options.
plan 53 tests now
changelog

Fixes #896
Merge branch 'pr/896' into devel
changed path to path_info
Changelog
Merge branch 'pr/903' into devel

Fixes #902
Fixes #903
add plan to subtest
Merge branch 'issue/901' into devel

Fixes #901
update CHANGES + version