Remove the hugo-nav function

Remove the hugo-nav since it relied on a slow library.  The current
build reimplements the absurl functionality based on string replace.
Discovered that my prior implementation missed the requirement for
making absolute paths (/path) absolute with the host, whereas a relative
path is left untouched.  Updated the test cases to support this if this
is reimplemented.

hugolib/site.go

@@ -576,19 +576,11 @@ func (s *Site) render(d interface{}, out string, layouts ...string) (err error)
 		return
 	}
 
-
-	section := ""
-	if page, ok := d.(*Page); ok {
-		section, _ = page.RelPermalink()
-	}
-
 	absURL, err := transform.AbsURL(s.Config.BaseUrl)
 	if err != nil {
 		return
 	}
-	transformer := transform.NewChain(
-		append(absURL, transform.NavActive(section, "hugo-nav")...)...,
-	)
+	transformer := transform.NewChain(absURL...)
 
 	var renderBuffer *bytes.Buffer