Fixed a few small spelling errors.

YoutubeExtractor/YoutubeExtractor/DownloadUrlResolver.cs

@@ -20,7 +20,7 @@ public static class DownloadUrlResolver
         /// to the decrypted URL. Use this method, if you have decryptSignature in the <see
         /// cref="GetDownloadUrls" /> method set to false.
         /// </summary>
-        /// <param name="videoInfo">The video info which's downlaod URL should be decrypted.</param>
+        /// <param name="videoInfo">The video info which's download URL should be decrypted.</param>
         /// <exception cref="YoutubeParseException">
         /// There was an error while deciphering the signature.
         /// </exception>
@@ -331,4 +331,4 @@ private class ExtractionInfo
             public Uri Uri { get; set; }
         }
     }
-}
+}

YoutubeExtractor/YoutubeExtractor/VideoDownloader.cs

@@ -21,7 +21,7 @@ public VideoDownloader(VideoInfo video, string savePath, int? bytesToDownload =
         { }
 
         /// <summary>
-        /// Occurs when the downlaod progress of the video file has changed.
+        /// Occurs when the download progress of the video file has changed.
         /// </summary>
         public event EventHandler<ProgressEventArgs> DownloadProgressChanged;
 
@@ -78,4 +78,4 @@ public override void Execute()
             this.OnDownloadFinished(EventArgs.Empty);
         }
     }
-}
+}