add to string for any

Author: longbai

library/src/main/java/com/qiniu/android/bigdata/pipeline/Point.java

@@ -117,6 +117,8 @@ void appendAny(String k, Object v) {
  append(k, (Map) v);
  } else if (v instanceof Date) {
  append(k, (Date) v);
+ } else {
+ append(k, v.toString());
  }
  }