Update gem configuration

Run `ore` against the directory and merge in various bits and pieces
that are more in line with current gem practices, including:

* documentation
* rake test runner
* gem dependencies
* rubygems-tasks
* gemspec configuration
* add Changelog
Update quoting style
Update travis config
Allow jruby Travis failures because of C exts
WIP rbx support
Merge pull request #7 from newleaders/gem-update

Gem configuration update