2.0.0
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- Replaced deprecated `optimist` with `minimist`.
- Added test coverage.
- Dropped `node@0.8` support.
- Added build for `node` versions: `io.js`, `4.2`, `5.x`.
- Added tests for windows environment.
- Made `.arg` layer writable.
- Support `undefined` setter argument to remove the variable from specific layer.

1.0.0
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- Initial release.