Port bug fix for clobbered assets

[fotinakis]

Hello! We fixed a high-priority asset discovery bug in ember-percy and noticed that the gatherBuildResources method was also duplicated into this project with the same bug present.

The bug is present here:

percy-node/src/percy-node-client.js

Line 391 in 3ec0c2d

function gatherBuildResources(percyClient, buildDirs, rootDirs) {

You should upgrade percy-client to 2.10.0, and then remove gatherBuildResources entirely and use the new method present on PercyClient objects: percyClient.gatherBuildResources.

See here for a reference bugfix from ember-percy: percy/percy-ember#70

Key to note: the method now returns an array, instead of a hash. If you need the hash you'll want to construct it in the same way as in the above reference.