update README

README.rst

@@ -2,38 +2,49 @@
 gallery-dl
 ==========
 
-gallery-dl is a image gallery downloader for several image hosting platforms.
+*gallery-dl* is a small command-line tool to download images and entire image galleries from several image hosting platforms.
 
 Installation
-------------
+============
 
-Via pip:
+You can install *gallery-dl* with pip:
 
 .. code:: bash
 
     $ pip install gallery-dl
 
-Or from github:
+or directly from github:
 
 .. code:: bash
 
     $ git clone https://github.com/mikf/gallery-dl.git
     $ cd gallery-dl
     $ python3 setup.py install
 
+Supported Sites
+===============
+
+* images (and ugoira) per artist from pixiv, nijie, deviantart
+* images per tag from booru-like sites (danbooru, gelbooru, chan.sankakucomplex, yandere, konachan, safebooru, 3dbooru, e621)
+* manga chapters from batoto, kissmanga, mangapanda, mangareader, mangastream, powermanga, redhawkscans
+* galleries from exhentai, nhentai, hitomi
+* images and videos from threads on Futaba Channel-like boards (4chan, 8chan)
+
 Usage
------
+=====
 
 .. code:: bash
 
     $ gallery-dl URL [URL...]
 
+Certain supported sites require authentication to download images from. This currently includes pixiv, exhentai, gelbooru and nijie. To make these sites accessible to *gallery-dl* you need to specify the necessary login credentials or cookies in the configuration files.
+
 Configuration
--------------
+=============
 
 Configuration files for gallery-dl use a JSON-based file format. For a (more or less) complete example, see gallery-dl.conf_.
 
-gallery-dl searches for configuration files in the following paths:
+*gallery-dl* searches for configuration files in the following paths:
 
 * /etc/gallery-dl.conf
 * ~/.config/gallery/config.json