Features

• Use _.create in .extend Use _.create in extend #3553
• Add #findIndex and #findLastIndex to Collection Add findIndex and findLastIndex underscore methods to Collection. #3811

Bug Fixes

• #_removeModels model still in collection regression Fix _removeModels regression #3803
• #set model id regression Fix 1.2.2 Model#id regression #3833
• #remove returning false regression Always return removed array from #_removeModels #3837
• #reduce and friends regression Add reduce to deopted methods #3820

Maybe

• Deopt Underscore methods containing arguments Deopt Underscore methods that use arguments #3840
• Add #preinitialize Add a preinitialize method to allow for true instance properties and ES6 classes #3827
• Add update event feedback adding feedback to update event of collection #3711
• Object.prototype conflicts with _.defaults Avoid Object.prototype collisions with defaults #3843

/cc @paulfalgout. 😄