webpack 1.0 compatibility

Hi, @sokra.

I'm in a process of migrating require.js project to webpack. I'm studying your work for a week. I'm quite impressed by quality and amount of your work.

This project is in a rough state. I've spent an hour to fix errors occuring just on my project until successful svg output.

I've tested it with webpack@1.0.0-rc3, and 1 project (374 modules/1.6 MB of non-compressed JS).

__Do not merge this immediately.__ I guess you're not maintaining this actively. So I could make more fixes under your guidance in this branch. Only after that I suppose you should merge it.

Tests are needed badly. What testing libs do you prefer? I might put some basic tests here. I would go with mocha+should.js.

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Wrapping up.

1. What else should I fix?
2. Let's discuss tests.
3. Is there spec for `webpack --json`?