wrong image file name convertion when there are spaces in file name

[dracodoc]

I have a image file with spaces in name (they are generated from knitr automatically so it's unpractical for me to remove the space manually every time). I put the image file under the post asset folder, use this to refer the image in markdown file:

![plot of chunk Basic Module Detector Alert](Basic Module Detector Alert-1.png) 

After post generation, the html is referring the image like this:

<img src="Basic Module Detector Alert-1.png" alt="plot of chunk Basic Module Detector Alert"> 

But the image file in public folder was renamed with all spaces replaced by %20, thus the image cannot be displayed.

Either the image file should not be renamed, or the html should use renamed file name.

[Xuanwo]

I think we should use renamed filename in html.

[leesei]

Global asset (/source/assets)

File was not renamed in public and can be accessed with src with space in link.

Although it works currently, we should ALWAYS urlescape links in HTML.

Post asset

Renaming the file (cat image.png -> cat%20image.png) make it accessible only with cat%2520image.png.
This renaming should not have done in the first place.

[leesei]

Use {% asset_img "spaced asset" "spaced title" %} to access spaced asset.