Avoid splitting words for summary

Avoid splitting words for summary

For people using autogenerated summaries, this is one of the hot spots in the memory department.

We don't need to split al the content into words to do proper summary truncation.

This is obviously more effective:

```
BenchmarkTestTruncateWordsToWholeSentence-4            300000          4720 ns/op           0 B/op           0 allocs/op
BenchmarkTestTruncateWordsToWholeSentenceOld-4         100000         17699 ns/op        3072 B/op           3 allocs/op
```