docs(warpPerspective): enhance with Kino and some text

[mnishiguchi]

Some enhancement to the warpPerspective notebook. Here are some of the things this PR explores.

• Use some cool features of newer Kino
• Remove the Livebook output
• Make variables slightly more human friendly
• Save the downloaded file to a tmp dir instead of current dir
• Use the Cv alias as in some other documents
• etc

[cocoa-xu]

Thank you! :)