Dependency upgrades

[mixonic]

I'm having trouble running ember try:each locally and tried an upgrade of clean things up. This patch results in a different error:

EslintValidationFilter can only handle one:* broccoli nodes, but part of the given input pipeline is a many:* node. (broccoli-merge-trees is an example of a many:* node) Please perform many:* operations after linting.

Which I presume is related to the way this project modifies the test tree in ember-cli-build.js.

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edit: This PR now upgrades Ember-CLI without adding ember-cli-eslint. The repo is bit by ember-cli/ember-cli-eslint#56 which seems related to the testTrees merged tree in index.js.