Make the title case style guide configurable

This works for the `title` func and the other places where Hugo makes title case.

* AP style (new default)
* Chicago style
* Go style (what we have today)

Fixes #989

tpl/strings/strings_test.go

@@ -19,11 +19,12 @@ import (
 	"testing"
 
 	"github.com/gohugoio/hugo/deps"
+	"github.com/spf13/viper"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-var ns = New(&deps.Deps{})
+var ns = New(&deps.Deps{Cfg: viper.New()})
 
 type tstNoStringer struct{}