Github user 1ambda commented on the issue:
https://github.com/apache/zeppelin/pull/1659

@bzz Thanks for review! Things you pointed out are very important. So I'v
done some research about node and npm
The above screenshot is about LTS schedule.
- Some apache projects use 4.x. but Active LTS will be end before 2017.04.
So they (should) move to 6.x If they care about what they are building.
- I used node [6.9.1](https://nodejs.org/en/blog/release/) in this PR. This
is one of LTS version for 6.x that means, it (6.x) is somewhat stabilised.
([6.0.0 released in 2016.04](https://nodejs.org/en/blog/release/v6.0.0/))
- **Basically, we use node as a tool**. **not the runtime**. In other
words, we need something can boost our productivity instead of old one. For
example, writing to build tools easily using es2015 or supporting fast
compilation. ([6.9.1 supports es2015 99%](http://node.green/))
Regard to npm
- [npm 3.0.0 allow us to our dependencies to be installed maximally
flat](https://github.com/npm/npm/releases/tag/v3.0.0). (will increasing
download speed + support cache functionalities)
- So we might use [node 5.x which shipped npm
3.x](https://nodejs.org/en/blog/release/v5.0.0/) but 5.x is not LTS
- So use 3.10.10 which is the most recent one. Even, we can use
[4.0.3](https://github.com/npm/npm/releases) just released 2 days ago
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