Site retirement: Generic image/html for embedding

[timdream]

Our users were offered custom image for embedding. Per what's agreed, we'll need to replace them with a generic one. It'll need to have the same dimensions.

• https://gfx.tw/userstickers/0/1/featurecard.html (200x250)
• https://gfx.tw/userstickers/0/1/featurecard.png (200x250)
• https://gfx.tw/userstickers/0/1/featurecard-h.png (468x60)
• https://gfx.tw/userstickers/0/1/smallsticker2.png (165x90)
• https://gfx.tw/userstickers/0/1/smallsticker.png (200x100)

[timdream]

https://github.com/moztw/gfx.tw/tree/retirement Fixed here, to deploy on Aug 1 2017.

[timdream]

Merged to master and tested with above URL.