`pretty_generate` in `dump` out.
Forgot to add json to tcp/udp input format
Merge pull request #138 from fluent/pretty_format_for_last_updated

"Pretty" format for last_updated.json
Update required Ruby version to >= 1.9.3
Merge pull request #140 from ento/update-ruby-version

Update required Ruby version to >= 1.9.3
Add 'only 64 bit' note to Ubuntu 14.04
Bundler is required to build from source.

ref #117
Update last updated.

And, I've  applied the "pretty" format(ref #138).