Entities not receiving id properties

[flimshaw]

Hey there, thanks for the sweet library, exactly what I was looking for.

I looked through the code, and it seems like you have .id properties on Entity objects in the latest version on github, but what installed from NPM seems to be an older version. Both have 2.0.0 listed in package.json, but the one NPM installs doesn't include the .id property, and I'm sure other lovely improvements as well.