Improve TotalWords counter func

It is obviously more efficient when we do not care about the actual words.

```
BenchmarkTotalWords-4            100000         18795 ns/op           0 B/op           0 allocs/op
BenchmarkTotalWordsOld-4          30000         46751 ns/op        6400 B/op           1 allocs/op
```

hugolib/page.go

@@ -486,10 +486,6 @@ func (p *Page) ReadFrom(buf io.Reader) (int64, error) {
 }
 
 func (p *Page) analyzePage() {
-	// TODO(bep)
-	if true {
-		return
-	}
 	if p.isCJKLanguage {
 		p.WordCount = 0
 		for _, word := range p.PlainWords() {