Support for 2.x

[charleswong28]

ref: issue 43

• Added 3 folders for 1.x, 2.0.0, 2.3.3 at root. Hope it will be easier for the others to find.
• Modified the code structure a bit to help debug easier.
• I've disabled objectCaching for the text since when the group is scaled, the cache is not updated and the text will look blurry. This may not be a good solution. Look forward if someone is familiar with fabricjs 2.0 cache mechanism to modify it.
• Save and reload from JSON is not working on this pull request. I saw there is another pull request on this.

ref: issue 26

• Added globalCompositeOperation in delegatedProperties.

[c-gross]

Just tested your version for 2.3.3 . It's working but I have one issue.
I implemented some position horizontal center method to my text elements whichw as working with old fabric 1.5.0 and is also working in the lastest version. I was working with this curved extension in 1.5.0 but in 2.3.4 and this version of the extension the text is moving a little bit right.

item.set('left', config.pos_x - item.getScaledWidth() * Math.cos(angleRad) / 2);

Any idea why the calculation does not work for this version?

[charleswong28]

I also realized the padding of the curved text and the sharpness of the text are not the same in 1.x and 2.3.3 version. I believe the text class is modified in fabric 2.x and that's why the result is not the same.

Will look into this later when I have time!