feat(tour) initial content

@jbenet please review

If this is a desirable format, I will put in the rest so we can start to
make incrementatl progress on the actual copy.

Separated content from topic so Ids can be seen and modified without
excessive scrolling. Hopefully will make it easy to re-order content.

tour/all.go

 package tour
 
-import "sort"
+import (
+	"sort"
+
+	c "github.com/jbenet/go-ipfs/tour/content"
+)
 
 func init() {
 	for _, t := range allTopics {
@@ -14,13 +18,15 @@ func init() {
 // Topics contains a mapping of Tour Topic ID to Topic
 var allTopics = []Topic{
 	Topic{
-		ID:    ID("0"),
-		Title: "Hello Mars",
-		Text:  "Hello Mars",
+		ID:      ID("0.0"),
+		Content: c.IntroHelloMars,
 	},
 	Topic{
 		ID:      ID("0.1"),
-		Title: "Hello Mars 2",
-		Text:  "Hello Mars 2",
+		Content: c.IntroTour,
+	},
+	Topic{
+		ID:      ID("0.2"),
+		Content: c.IntroAboutIpfs,
 	},
 }

tour/content/introduction.go

+package content
+
+var IntroHelloMars = Content{
+	Title: "Hello Mars",
+	Text: `
+	check things work
+	`,
+}
+
+var IntroTour = Content{
+	Title: "Hello Mars",
+	Text: `
+	how this works
+	`,
+}
+
+var IntroAboutIpfs = Content{
+	Title: "About IPFS",
+}

tour/tour.go

@@ -4,6 +4,7 @@ import (
 	"strconv"
 	"strings"
 
+	content "github.com/jbenet/go-ipfs/tour/content"
 	u "github.com/jbenet/go-ipfs/util"
 )
 
@@ -27,8 +28,7 @@ func (a IDSlice) Less(i, j int) bool { return a[i].LessThan(a[j]) }
 // Topic is a type of objects that structures a tour topic.
 type Topic struct {
 	ID ID
-	Title string
-	Text  string
+	content.Content
 }
 
 // Topics is a sorted list of topic IDs