Don't install node modules locally

[DarkDust]

Currently, the check-and-run-apollo-cli.sh script automatically installs the missing Apollo node module and its dependencies locally if they're missing. I would prefer the script would not do that but instead exit with a helpful error message.

I was thinking about generating a pull request to patch the script to optionally exit instead of installing automatically but wasn't able to come up with a good solution for that and would like to discuss options here first.

So far I came up with three ideas:

1. Make the script support an environment variable that controls whether to exit or install.
   • Easy to do, easy to integrate into the Run Script phase, but still feels odd and like users are easy to miss this.
2. Make the script support a command line argument to control whether to exit or install.
   • Harder to do, would need to filter out that argument before passing to apollo codegen:generate. It might create a lot of confusion.
3. Create a new script that behaves differently.
   • Would need to refactor the existing script so both can share most of the code; not very hard. The difference in behavior would be very obvious.

So far I think a new script might be a good idea. Thoughts?

[designatednerd]

This definitely seems like something that'd require an updated build script. I am looking at making some significant changes around this because we want to handle things like not regenerating if it's not required, but I don't have an ETA. I'll definitely keep this in mind as I make those changes though.

[designatednerd]

Note mostly to self: Need to look at whether to switch back to only requiring a major version of node rather than pinning to an exact one.

[designatednerd]

This should now be greatly improved with 0.16.0, which basically removes any need to use NPM.

Please check out our updated installation instructions for setting up a build script for full details. Thank you!