code: public static InputStream fileAsStream(String filename) {
      File classpathFile = getClasspathFile(filename);
      return fileAsStream(classpathFile);
    }
docs: Returns the input stream of a file with specified filename
  
  @param filename the name of a {@link File} to load
  @return the file content as input stream
  @throws IoUtilException if the file cannot be loaded