Chrome Web Store promotional images

I've began work on the promotional images with the logo.
The old logo had some issues with the bottom-left ending of the Q bowl/circle, and with the curves on the Q tail. I've redrawn the logo as SVG and improved these.

- [x] Logo improvements
- [x] Small image
- [x] Large image
- [x] Marquee image

You can take a look at `artwork/quicktext-icon.png` to see a comparison of the old and new logo.
What do you think? Do you like the new logo better, or should I use the older one, without my changes, in the promotional images?