Allow duplicate keys

[jordanbtucker]

Fixes #57

[aeisenberg]

Thanks for the pull request! The travis CI build has failed, but it doesn't look like it's anything related to your PR. The commits look good and I would like to merge, but I don't want to until we have a clean build. Would you mind pushing again and seeing if this is a transient problem?

[jordanbtucker]

I think the problem is with the develop branch. .travis.yml lists a Node version of 0.9, but the travis CI VM doesn't have 0.9 installed.

[aeisenberg]

Looks like that's right. But, this build was working in the past. Perhaps this particular build node is not the same as the others and doesn't have 0.9 installed (while the others do).

[jordanbtucker]

Looks like you can trigger a re-run of a Travis CI build if you're logged in.

[aseemk]

Thanks for fixing the build issue! @jordanbtucker, do you know how to git rebase? If you rebase this branch to the latest master now, the CI should pass again.

We should add a CONTRIBUTING.md, but as a matter of habit, it's always nice to rebase branches/pull requests before merging them, to ensure clean merges (not just logistically but logically too).

[aseemk]

Minor: 4-spaces here too.

[jordanbtucker]

Thanks for the rebase tip.