Handle undefined values on not found key warning

This fixes the not found key warning when a property is not defined in the scope:

var scope = new Scope({});

var scopeKeyData = scope.computeData("foo.length", {
   warnOnMissingKey: true
});

scopeKeyData.read();  // -> Unable to find key "foo.length".

#210

Improve the “unable to find key” warning

Improves the missing key warning by logging of the property that can read for example:

var context = { foo: true };

var scope = new Scope(context);
var scopeKeyData = scope.computeData("foo.length", {
   warnOnMissingKey: true
});

scopeKeyData.read();  // -> Unable to find key "foo.length". Found "foo" with value: true

Add links to scope.root deprecation warning

#209

Implement can.setElement symbol

v4.13.3

4.13.3

Removing unnecessary properties from LetContext.prototype

Previously the LetContext had properties like one that would prevent you from ever using these keys in a Scope. This removes properties that are not needed from LetContext.prototype and only leaves required properties and Symbols.

#205

QUNIT2 upgrade

This updates the tests to use QUnit@2.x.x.

#202

scope.args

scope.args added as a "fixed" version of scope.arguments

initialValue should not emit ObservationRecords

Issue: #198

scopeKeyData.initialValue //-> should not emit a observationRecord 

Lazy Initialization and supporting primitive reads

#197 fixes someProperty.split('').reverse().join()

#196 new ScopeKeyData can be passed a warnOnMissingKey option. This will warn if a value is missing. Also, ScopeKeyData is lazy now.

Handle reads during queue execution

Issue: #194

There was a problem with a two-way binding where the parent was undefined and the child had a value:

<my-child childValue:bind="parentValue"/>

A semaphore warning was being produced.