Code cleanup

#156

This fixes setting property value to null or undefined, for example:

class Foo extends ObservableObject() {
    static get props() {
       return {
	 nullProp: { default: null },
	 undefinedProp: { default: undefined }
      };
   }
}
var foo = new Foo();
foo.nullProp // -> null
foo.undefinedProp // -> undefined

and

class Foo extends ObservableObject() {
    static get props() {
       return {
	 nullProp:  null ,
	 undefinedProp: undefined
      };
   }
}
var foo = new Foo();
foo.nullProp // -> null
foo.undefinedProp // -> undefined

#154

This fixes the test for type errors in order to make CanJS test suite pass.

This catchs can-type error to check the presence of .type property in order to use it for message improvements.

#149

This patch release fixes .update and updateDeep behavior when called on list-like objects.

The following code was throwing an exception due to both methods always calling canReflect.updateMap and canReflect.updateDeepMap under the hood even if the caller was an array.

class MyArray extends mixinMapProps(Array) {}
let arr = new MyArray();
arr.push(1, 2, 3, 4);
assert.equal(arr.length, 4); 
arr.updateDeep([]); // throws an exception
assert.equal(arr.length, 0);

This enhance type error message by adding the value type in the message:

Before:

farah.age = '4'; // -> Uncaught Error: 4 is not of type Number. Property age is using "type: Number". Use "age: type.convert(Number)" to automatically convert values to Numbers when setting the "age" property.
`

Now:
farah.age = '4'; // -> Uncaught Error: "4" (string) is not of type Number. Property age is using "type: Number". Use "age: type.convert(Number)" to automatically convert values to Numbers when setting the "age" property.

#143

list property will have Array type with an example like the following:

class Foo extends mixinObject() {
     static get props() {
          return {
             list: []
          };
     }
 }
var foo = new Foo();
foo.list = [ "one", "two" ]; 

TypeError: Right-hand side of 'instanceof' error will not be thrown.

#141

This improve the error message bu suggestion to use type.convert for the right type:

class Person extends mixinObject() {
    static get props() {
       return {
         age: type.check(Number)
       };
    }
}
var farah = new Person();
farah.age = '4'; // -> `Uncaught Error: 4 is not of type Number. Property age is using "type: Number". Use "age: type.convert(Number)" to automatically convert values to Numbers when setting the "age" property.`

#140

#136

#131