add code to restore saved clipPath

[AlexSergey]

After I saved example 8 from clipPath:
http://fabricjs.com/clippath-part3
"Clipping the canvas"
I tried to restore it from loadFromJSON. But in this method isn't process clip path. I added some code to fix it.

[asturur]

didn't we fix this recently? i remember a pr about this.

[AlexSergey]

I found only save fix, where it was replaced from:
data.clipPath = this._toObjectMethod(clipPath, methodName, propertiesToInclude);
to:
data.clipPath = this._toObject(clipPath, methodName, propertiesToInclude);

But restore method is not support clipPath restore to the canvas.

[asturur]

great. i ll look at it soon.

[asturur]

i want to merge it, but i would like a test too. trying to add it tomorrow since i want to head to a release

[asturur]

ok merging it!
i ll add tests in a pr shortly