Merge pull request #72 from square/jw/unused

Remove unused ServerException.

http/src/main/java/retrofit/http/ServerException.java

-// Copyright 2010 Square, Inc.
-package retrofit.http;
-
-/**
- * Thrown if the server behaves unexpectedly. Typically, this indicates an
- * intermittent problem; the request can be retried again later.
- *
- * @author Bob Lee (bob@squareup.com)
- */
-public class ServerException extends Exception {
-
-  public ServerException(String detailMessage) {
-    super(detailMessage);
-  }
-
-  public ServerException(Throwable throwable) {
-    super(throwable);
-  }
-}