Prepare release 3.2.0

[vincent-psarga]

Note: this should not be merged back to master, simply do a release with:

• Fix issue json-reporter: do not fail when embedding byte strings #1388 (which should help with Ruby CCK)
• Backport the --out url option so people who still use cucumber-ruby 3.x should be able to push report easily (Updates for --out=url option #1406 and Support --out http://.... #1395)

[vincent-psarga]

So there's no Webrick available for Ruby 2.2 apparently (ruby/webrick@6259c37 - it used to support 2.5+ and went down to 2.3 if I understand this correctly).

I'm puzzled on how to handle that:

• do a release knowing that we have a dev_dependency failing for Ruby 2.2 (which EOL was 2 years ago) ?
• remove the tests related to the --out=url option that rely on Webrick (knowing that this will be the last 3.x release on cucumber-ruby and work will now be done on master where we still have the tests working)