Upgrade to ember 2.15 triggers this message

Hi there,

I got this message coming from **broccoli-babel-transpiler** when I upgraded my ember app to ember 2.15.0

```javascript
broccoli-babel-transpiler is opting out of caching due to a plugin that does not provide a caching strategy: `function () {
return {
visitor: {
VariableDeclaration: function VariableDeclaration(path, file) {
var node = path.node,
parent = path.parent,
scope = path.scope;

if (!isBlockScoped(node)) return;
convertBlockScopedToVar(path, null, parent, scope, true);

if (node._tdzThis) {
var nodes = [node];

for (var i = 0; i < node.declarations.length; i++) {
var decl = node.declarations[i];
if (decl.init) {
var assign = t.assignmentExpression("=", decl.id, decl.init);
assign._ignoreBlockScopingTDZ = true;
nodes.push(t.expressionStatement(assign));
}
decl.init = file.addHelper("temporalUndefined");
}

node._blockHoist = 2;

if (path.isCompletionRecord()) {
nodes.push(t.expressionStatement(scope.buildUndefinedNode()));
}

path.replaceWithMultiple(nodes);
}
},
Loop: function Loop(path, file) {
var node = path.node,
parent = path.parent,
scope = path.scope;

t.ensureBlock(node);
var blockScoping = new BlockScoping(path, path.get("body"), parent, scope, file);
var replace = blockScoping.run();
if (replace) path.replaceWith(replace);
},
CatchClause: function CatchClause(path, file) {
var parent = path.parent,
scope = path.scope;

var blockScoping = new BlockScoping(null, path.get("body"), parent, scope, file);
blockScoping.run();
},
"BlockStatement|SwitchStatement|Program": function BlockStatementSwitchStatementProgram(path, file) {
if (!ignoreBlock(path)) {
var blockScoping = new BlockScoping(null, path, path.parent, path.scope, file);
blockScoping.run();
}
}
}
};
}`.
```