[Enhancement]: Passing the url of the image to the pipeline directly instead running wget first

[Chiiizzzy]

The ERROR Read image towhee_logo.png failed has been reported several times, many users might forget to run the prep work in quick start. Since the file directory and url are supported, shall we consider using the url in quick start?

[fzliu]

Made some changes to the quick start guide in #132. If that look sufficient, please close this issue.