fix default cache size

Author: wlq

library/src/main/java/com/danikula/videocache/HttpProxyCacheServer.java

@@ -359,7 +359,7 @@ public Boolean call() throws Exception {
      */
     public static final class Builder {
 
-        private static final long DEFAULT_MAX_SIZE = 512 * 104 * 1024;
+        private static final long DEFAULT_MAX_SIZE = 512 * 1024 * 1024;
 
         private File cacheRoot;
         private FileNameGenerator fileNameGenerator;