Support for `.` ?

`ffmpeg(1)` allows you to supply the start time to seek the video to in terms of sub-seconds. For example: `00:00:00.104`.

Right now `timecodeutils` rounds, which is somewhat unexpected, and potentially better left to do to the developer if desired:

``` js
> require('timecodeutils').secondsToTC(.104)
'00:00:00'
```
