updated activesupport include catch 5.0 rails

[thealexauer]

I updated the gemspec, so it could work with Ruby on Rails 5.0, which requires ActiveSupport 5.0

The parsing works for me.

[gmodarelli]

Hi @dompstar, thanks for the contribution.

I'm willing to merge the PR but the problem is that activesupport 5 requires Ruby version => 2.2.2

If you specify Ruby 2.2.2 in the xml2json.gemspec as the minimum Ruby version supported I'm ok with merging it and release the gem under a new tag. Please also specify this in the README.md.

One more thing. I realized that I had mistakenly committed and pushed the Gemfile.lock and it is causing Travis to fail the build. I removed it from master so if you remove it also from your fork we will have Travis passing also for this PR.

Thank you