Fix seconds parsing #2209
Creating a milliseconds entry by doing math on the seconds entry:

```
msecs = round(float(seconds[i] % 1)*10**6)
```

Can you add some test cases for this? Thanks.
 Would love to, but I can't find your date parsing tests? Can you give me a pointer? If you don't have any date parsing tests yet, I'm afraid it's out of my league, as I never wrote a unittest before, but I'm sure I could extend existing ones.
 Oh sure thing, please check pandas/io/tests/test_date_converters.py
`test_datetime_six_cols` uses the converter that calls `lib.try_parse_datetime_components`
