Failing tests and crashing since 0.2.0

[ghost]

Hi,

I've noticed that the package fails 10/82 tests in versions 0.2.0, 0.2.1 and 0.2.2.
However, more severely, it also seems to crash the npm republish script.

I tried to debug it but the error message is very vague. Here is the error log I received.

Hope that helps and keep up the good work on v4.0!

[mbostock]

Sorry; I had been testing against an old version of d3-dsv, which now exposes a columns field on the loaded data as of version 0.1.10.