deprecation warning in embercli 2.18.0

[crotwell]

ember install ember-async-button generates a deprecation warning in ember 2.18.0:

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 }).

I believe updating ember-cli-babel to 6.11.0 will fix this as 6.8.2 depends on an older version of ember-cli-version-checker.

[tamzinblake]

Fixing this will also require upgrading ember-cli-htmlbars