Add JSON output support

implement Test::BDD::Cucumber::Harness::JSON

so that it is possible to display data in tools like
"Publish pretty cucumber reports"
(https://github.com/masterthought/cucumber-reporting)
that parse JSON output file.
Fix wrongly calculated step duration

it should be in nanoseconds
Force change id to text value in Cucumber JSON output

in Test::BDD::Cucumber::Harness::JSON

so that Jenkins publisher plugin does not fail when it parses "id".
Report result "undefined" as "skipped" in JSON

because "undefined" is used from skipped and missing tests
Set JSON arguments (utf8=>1, pretty=>1) by default

in Test::BDD::Cucumber::Harness:JSON
Write tests for Test::BDD::Cucumber::Harness::JSON
Fix building of description in Harness JSON

remove wrongly used $line->content_remove_indentation",
use $line->content instead.
Merge pull request #38 from tomas-zemres/master

Add JSON output support