Returns the version as a Gem::Version
Allow accessing dimension attributes with strings

Fixes #232
Add the `debug` mode and note timeout

Fixes #229
Fix Travis build for Rubinius

Installing gems with RubyGems <= 2.4.0 is not thread-safe, and because
of that Rubinius was failing when installing gems. The latest RubyGems,
2.4.1, allegedly fixes that problem, so I added

  gem update --system 2.4.1

to the Travis build. But that didn't work, the error was still there.
So I decided to just not install gems in parallel, and cache the
installed gems, so that step should still be fast enough.
Merge pull request #247 from janko-m/fix-rubinius-travis

Fix Travis build for Rubinius
Merge pull request #246 from janko-m/improve-debugging

Add the `debug` mode and note timeout
Merge pull request #245 from janko-m/fix-string-keys

Allow accessing dimension attributes with strings
Fix Rubinius on Travis by upgrading Rubinius
Merge pull request #233 from futhr/versioning

Returns the version as a Gem::Version