Merge in_tail_ex features into in_tail. refs #269

Last step of #269 , merge in_tail_ex into in_tail.
The different from original in_tail_ex is below:

- `refresh_interval` is `60` by default. The user should set `refresh_interval XXs` for watching new files
- expand_date is always `true`
- `read_from_head` is `false` by default. So you should set `true` when emulates original `in_tail_ex`.

This pull request changes in_tail internal, so I need some testers.

## UPDATED (Mar/28/2014)

refresh_interval changed from `nil` to `60` seconds.