fix #19: remove download URL

setup.py

@@ -17,7 +17,6 @@ setup(
     author = proj_info['author'],
     author_email = proj_info['author_email'],
     url = proj_info['url'],
-    download_url = proj_info['download_url'],
     license = proj_info['license'],
     
     description = proj_info['description'],

you-get.json

@@ -6,7 +6,6 @@
     "author": "Mort Yao",
     "author_email": "mort.yao@gmail.com",
     "url": "http://www.soimort.org/you-get/",
-    "download_url": "https://github.com/soimort/you-get/zipball/master",
     "license": "MIT",
     
     "description": "A YouTube/Youku video downloader written in Python 3.",