update package's node + twigjs versions; update travis's node versions; bump

[olets]

Updates to the latest twig.js

---

This PR has gotten bigger. Updated description:

The main purpose of this PR is to use the latest 1.x.y version of twig.js

gulp-twig's node requirements have fallen far enough behind twig.js's that updating to the latest twig.js makes gulp-twig's tests fail. So this PR also updates node in package.json and .travis.yml.

Upping the node version dependency should be considered a breaking change, so I've bumped to v1. This has the perk of fitting nicely with twig.js's versioning. I propose that gulp-twig's major version should always be the same as the major version of the twig.js dependency.

[ryuran]

Twig.js v1.10.4 is released
#32 and #34 are exactly for the same thing

[olets]

Sure is! Added 1 to the version specifically so that gulp-twig and anything else that uses twigjs as a dependency can specify semver ranges (which npm doesn't support for v<1.0.0).

Note gulp-twig's tests now fail (#35) but twigjs is passing so this should be safe to merge and use.

[ryuran]

We should change travis config (https://github.com/zimmen/gulp-twig/blob/master/.travis.yml) for recent node/npm.
And change node and npm minimal version in package.json.
We must up gulp-twig version to indicate new requirement.

[olets]

@ryuran good catch thanks

[bezoerb]

Why not change this to >=4.0 according Travis & Readme?

[olets]

Lifted this uncritically from twig.js. >=4.0 makes sense to me.

[bezoerb]

Would also add 8

[olets]

None of the dependencies test 8. twig.js tests 4 and 6. Since Twig is what we care about it makes sense to match its tests

[bezoerb]

good point :)

[bezoerb]

So let's merge this :)

[bezoerb]

@olets, @Dotmagic, @webrgp: i think we should consider #18, #19 and #21 before v1.0.0 release. What do you think?

[olets]

I think go with 1.0.0 now. For me, dependencies like this should follow semver - so bumping from 0.x to 1.0 is saying "there was a breaking change" not "we've ironed out the bugs." The upgraded node requirement is a breaking change.

If we do use a lower version, we'll have to remember to downgrade the version in package.json from the bump in f64df15