Add support for node v6

[bsudekum]

It's time to add support for node v6. I think this should be fairly straightforward quest:

• Verify no dependencies need to be updated for v6
• Update test matrix to begin testing both node v4 and v6
• Merge this
• Add new release with v6 binaries

/cc @tmpsantos @jfirebaugh @springmeyer

[bsudekum]

Unsure if this is the best way to add another version for bitrise to test.

[springmeyer]

@bsudekum looks like you are using {configuration} in the package.json but not passing --debug to node-pre-gyp when publishing. To avoid builds clobbering each other this is important. This is done in #8865. Perhaps you should test and merge #8865 first before adding this? Or focus just on node v6 and hit debug builds later.

[bsudekum]

The last todo is to figure out how to test and publish macos on node v6. Unfortunately bitrise does not support matrix builds like on travis. We have a few options here:

• Add more to the current bitrise workflow as done in 2db9a9c. This now unlinks node v4, links node v6 and then run tests again.
• Add a new bitrise app specifically for node v6
• Something else?

/cc @1ec5

[bsudekum]

Now that Node macOS is running tests for both v4 & v6, the total test time is increased by ~5m. @jfirebaugh how do you feel about this? What if we support v4 & v6 only for a few months to give developers a grace period to upgrade?

[jfirebaugh]

Yeah, providing we a plan to eventually deprecate node v4 support, I think this is reasonable. There will have to be some window where we support both.

[jfirebaugh]

after_success.sh is what performs the publish, so it needs to be run after both the node@4 and node@6 builds or otherwise only the latter will get published. Suggest something like:

make test-node && ./platform/node/scripts/after_success.sh

[jfirebaugh]

Unless there's a compelling reason to test the Node v6 debug build independently from Node v4 debug and Node v6 release, we can probably omit this row from the matrix.