Add cross-env

[wtgtybhertgeghgtwtg]

This will allow npm scripts to be run on Windows environments.

[mattkrick]

duplicate of #134
there's another way for windows users to make this work, right?

[wtgtybhertgeghgtwtg]

What I had been doing was changing, for example
"NODE_ENV=development node ./src/server/server.babel.js"
to
"set NODE_ENV=development&& node ./src/server/server.babel.js"
But I don't know if that'd work on other platforms. This seems to be the simplest way.

[mattkrick]

as an OSX/linux guy i'm biased, but i feel like adding another dependency that is OS-specific is more confusing than just having windows folks prefix their commands with 'set'. I'm not 100% opposed to it, but "set" is shorter & it's expressive, so you know what it does. As a new dev to this repo, I'd probably look up what cross-env does, then realize I don't need it & delete it from all the scripts as well as deps.

[wtgtybhertgeghgtwtg]

The problem with that is that it's not documented. And even if you do document it, Windows users who download the package have to find that document, then alter the package in order to use it.

[mattkrick]

I'm totally open to documenting it! Currently installing rethinkDB isn't documented for windows. We could add a little something to the readme that says how to install RethinkDB & adjust the scripts. I'm just very hesitant to add in OS-specific stuff, especially when it's an OS that no one will deploy on.

[wtgtybhertgeghgtwtg]

I don't think it's that big of a deal either way. But it is a devDependency for react-look, so wouldn't it be there either way once #141 gets done?

[mattkrick]

if it's a devDeop, nah. But it's not the size, it's having 1 more thing that meatier is directly responsible for + the mental overhead for a newcomer having to figure out what it is, what it does, and whether they need it or not. If a dependency has sub-dependencies, I don't really care about those because all I'm after is a black box with an API, I don't care how that is achieved. I could see how it'd be beneficial if someone developed on both windows & mac at the same time, and in those scenarios it's just 1 install away.