Windows Support

This is an alternative to PR jashkenas/docco#155 which supports Windows by replacing shell commands within the program.

This does not touch upon `Cakefile` which will remain unix-only, at least for now. Basically, Windows users can use docco, but not develop it... yet.

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On a side note; can `cake install` simply be replaced with `npm link` or `npm install -g`?