fix parsing dates with more than 3 digits for second fraction, resolves #67

[toy]

I finally got my hands on investigating why NetNewsWire has problems with dates produced by ruby rss library. Problem is that dates will be produced with 6 digits for second fraction and this will currently be parsed as timezone, so date will be thrown ahead by multiple hours and if date changes it will randomly change.

The simplest solution was to make the parser just ignore extra digits.