update to babel 6

[faassen]

Babel 6 has been released. We should look into updating to that.

[guusdk]

Now that Babel 6 is a default, following the guide will generate something like this:

$ babel-node
You have mistakenly installed the `babel` package, which is a no-op in Babel 6.
Babel's CLI commands have been moved from the `babel` package to the `babel-cli` package.

For the intended target of the tutorial (n00bs like me), this is highly confusing. ;)