Update Ember and family to 2.18

[backspace]

This is a first pass after a complex merge. I expect many
lint failures and deprecations.

I wonder whether we can just import the Airbnb ESLint config
rather than duplicating it?

[backspace]

There are two duplicate deprecation warnings when running the server:

DEPRECATION: An addon is trying to access project.nodeModulesPath. This is not a reliable way to discover npm modules. Instead, consider doing: require("resolve").sync(something, { basedir: project.root }). Accessed from:   NPMDependencyVersionChecker (/Users/b/Documents/Travis/travis-web/node_modules/ember-cli-version-checker/src/npm-dependency-version-checker.js:11:32)
DEPRECATION: An addon is trying to access project.nodeModulesPath. This is not a reliable way to discover npm modules. Instead, consider doing: require("resolve").sync(something, { basedir: project.root }). Accessed from:   NPMDependencyVersionChecker (/Users/b/Documents/Travis/travis-web/node_modules/ember-cli-version-checker/src/npm-dependency-version-checker.js:11:32)

From what I can tell, these come from addons that have an old version of ember-cli-version-checker. I updated the addons I could… meh

I haven’t looked at deprecations in the console yet.

[backspace]

This seems sufficient; I’ll merge and deploy tomorrow.

[drogus]

I'm super happy to see this, because I'd like us to try out 2 new things: Glimmer named arguments and ES5 getters