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Counterpart to https://github.com/conda/conda/pull/795

I will start work on a "CondaJS" with the same goal as this repo for Launcher/other such projects; this library will use Node when available and otherwise fall back on HTTP (any comments about how the REST API should be structured?)

Work in progress.

TODO:

- [x] `update`
- [x] `config` (`get`, `set`, `remove`, `remove_key`)
- [x] `launch`
- [x] `remove`
- [x] `info <package_name>`