smaller teaser count

This patch adds smaller character counts for teasers: 25, 50, 75 and 100.

25 is approx one line on a three col layout, or these famous fixed blog things. 50 on wider layouts and 75 is onle line on two col fluid layout. Hundred is about two lines on a lot of layouts. hort teasers often look ery good ni listings.

For example http://fixme.remixreading.org/taxonomy/term/31. Note that this is achieved with a hard string trim, we want this to be achieved with the theaser generation code, snice that is much nicer, it looks for spaces etc. Our code does not do that yet, while this patch does.