Added extra subreddit name compatibilty.

This allows `GetSubreddit` and `GetSubredditAsync` to handle subreddits with the format "/r/Subreddit/", with the slash at the end. This previously gave a not-very-informative 404 error.

Author: ericBG

RedditSharp/Reddit.cs

@@ -210,6 +210,7 @@ public Subreddit GetSubreddit(string name)
                 name = name.Substring(2);
             if (name.StartsWith("/r/"))
                 name = name.Substring(3);
+            name = name.TrimEnd("/");
             return GetThing<Subreddit>(string.Format(SubredditAboutUrl, name));
         }
 
@@ -224,6 +225,7 @@ public async Task<Subreddit> GetSubredditAsync(string name)
                 name = name.Substring(2);
             if (name.StartsWith("/r/"))
                 name = name.Substring(3);
+            name = name.TrimEnd("/");
             return await GetThingAsync<Subreddit>(string.Format(SubredditAboutUrl, name));
         }