Suggest installing enzyme as dev dependency

[JBallin]

No description provided.

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[bugzpodder]

This is expected as we don't recommend user installing dev-dependencies. Please see previous issues for an explanation. Thanks!

[JBallin]

Sorry for not finding those previous issues!

This comment in #2696 explains that Dan has thoughtfully considered this issue and has decided to keep everything in dependencies. While I have arguments otherwise (and don't feel like there's a good explanation given), I trust and respect his decision.

This is a good example of an issue that can be debated endlessly because there's very little technical arguments for and against. I've made a choice there and if you disagree, you can always move those few lines.