Put 'beforeProperty' breaks with indented properties. #89

    @Test
    void testPutBeforeIndentedProperty() throws IOException {
        final String given = "# header comment\n"
                + "\n"
                + "  # key comment\n"
                + "  key=val";
        final String expected = "# header comment\n"
                + "\n"
                + "put=putVal\n"
                + "  # key comment\n"
                + "  key=val";

        Properties p = Properties.loadProperties(new StringReader(given));
        p.put(p.beforeProperty("key"),"put", "putVal");
        expectStoreText(p, expected);
    }