The Problems I have found for lib/fluent/parser.rb

### ValuesParser is not delete the output of time key like other do so.  
Time key should be deleted when it has used for fluentd internal time like TSVParser, CSVParser do so.

### LabeledTSVParser error handling problem
The error of "time_format parameter is ignored" puts message to $log.warn.
It should raise ConfigError.

### The default of time_key for LabeledTSVParser
I think LabeledTSVParser should be 'time' for the default of `time_key`.
This behavior causes confusion and not same as ApacheParser, JSONParser and RegexpParser.
It cannot seamless upgrade from in_tail with regex or apache apache2 nginx and so on.
There configuration usualy have time_format but not it has time_key.  like http://ltsv.org/
If not 'time' for the default of `time_key`, it could result useing current time even thouth set time_format.

**footnote**
* ValuesParser was used by LabeledTSVParser, TSVParser, CSVParser