[io.js] Print a warning message if the user is not on io.js 2.x

[ide]

Detects if the user is on Node or io.js 1.x and prints a banner explaining how to upgrade. We probably should link to more detailed upgrade docs so this is just a start.

I also added a function to format banners that is kind of useful.

Addresses part of #1737

[prathamesh-sonpatki]

@ide I just tried

brew link iojs --force

But it gives following error for me

$ brew link iojs --force
Linking /usr/local/Cellar/iojs/2.3.1... Error: Could not symlink bin/node
Target /usr/local/bin/node
is a symlink belonging to node. You can unlink it:
brew unlink node
To force the link and overwrite all conflicting files:
brew link --overwrite iojs
To list all files that would be deleted:
brew link --overwrite --dry-run iojs

I think we should mention

brew unlink node

also.

[ide]

@prathamesh-sonpatki good catch. the instructions now include brew unlink node; brew install iojs && brew ln iojs --force.

[amasad]

awesome.

[ide]

Removed the bit about "next release" from the message since the jest upgrade and io.js support already landed. Moving fast!

[ide]

@amasad could I get an update on when this will be merged? I'd like to include it with 0.8.0-rc (checklist here #1864) to pre-emptively answer issues people might encounter if they're using Node.

[ide]

@nicklockwood could you help merge this in before we cut 0.8.0-rc? This is the last commit I'd like to include in the RC and the rest of the items on #1864's checklist can wait for 0.8.0-rc.2.

[nicklockwood]

@ide, I don't understand the JS side of the platform well enough to judge the implications of this. Maybe @vjeux or @tadeuzagallo can weigh in?

[tadeuzagallo]

LGTM

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[ide]

Thanks guys! Ready to release 0.8.0-rc very soon!