Support combined datetime format with subseconds (yyyyMMddhhmmss.SSS) 

We have support for a unixy combined timstamp format of the form `yyyyMMddhhmmss`

However, some systems log with subseconds appended, for example:
```
20140722105203.364
```
The above should parse as: `"2014-07-22 10:52:03.364 +0000 UTC"`

But parsing fails with the error:
```
parsing time "20140722105203.364": month out of range
```