Release version 0.2.0.

Use this issue to track progress of pre-release development.

Signal will be read for use with a version `0.2.0` release for developers who are able to keep up with a project in development. When `0.2.0` is released, Signal will follow the same release pattern as Node.js, with the even number indicating a API frozen maintenance branch, while development continues on the odd number one less than the even number.

That is, when `0.2.0` is release, the `0.2` version branch will be API frozen. Development will continue on `0.1` toward a `0.4.0` release. When `0.4.0` is released, it will be API frozen. The `0.3` branch will become the development branch. We continue in this fashion until a version `1.0`.

Prior to the `0.2.0` release, if you decide to adopt the pre-release `0.0` branch, please use NPM and `package.json` to freeze a version of Signal that works for you. Follow this issue for updates on changes. Read the change log to know how an update will affect your application.

When `0.2.0` is released [semantic versioning](http://semver.org/) takes over. Even numbers are API stable, odd numbers are API playgrounds. At `0.0`, however, everything is in flux. Up is down. Left is right. Callbacks are synchronous. Cats like baths. Early adoption is welcome, because it helps build a better library, but please be patient and please be careful.