refactor(tour0 move chapter to it's own file

tour/all.go

 package tour
 
-import (
-	"fmt"
-	"sort"
-)
+import "sort"
 
 func init() {
 	for _, t := range allTopics {
@@ -93,17 +90,3 @@ var FileBasicsMounting = Content{
 	Text: `ipfs mount (simple)
 	`,
 }
-
-// Chapter is used to define a chapter once and derive IDs for any number of
-// sections within.
-//
-// It's designed to make it easy to re-order chapters with minimal fuss.
-//
-// eg.
-// 		Intro := Chapter(1)
-// 		ID("1.1") == Intro(1)
-func Chapter(number int) func(topic int) ID {
-	return func(topic int) ID {
-		return ID(fmt.Sprintf("%d.%d", number, topic))
-	}
-}

tour/chapter.go

+import "fmt"
+
+// sections within.
+//
+// It's designed to make it easy to re-order chapters with minimal fuss.
+//
+// eg.
+// 		Intro := Chapter(1)
+// 		ID("1.1") == Intro(1)
+func Chapter(number int) func(topic int) ID {
+	return func(topic int) ID {
+		return ID(fmt.Sprintf("%d.%d", number, topic))
+	}
+}