Filter fsevents out of snapshots so Travis doesn't fail

The reify() method now returns the *actual* actualTree, so even though
engine-mismatching optional deps remain in the package-lock, they're not
being passed in the resolved tree.

Filter the offending darwin-only module out of the snapshots so that Travis
(which is Linux) doesn't fail tests.  In that case, just manually verify that
fsevents is actually in the package-lock, even though it isn't in the snapshot.

lib/arborist/reify.js

@@ -296,8 +296,8 @@ module.exports = cls => class Reifier extends Ideal(cls) {
   [_checkEngineAndPlatform] (node) {
     // engine/platform checks throw, so start the promise chain off first
     return Promise.resolve()
-     .then(() => this[_checkEngine](node))
-     .then(() => this[_checkPlatform](node))
+      .then(() => this[_checkEngine](node))
+      .then(() => this[_checkPlatform](node))
   }