Get now returns the *Item rather than the item's value. Get no longer actively

purges stale items.

Combining these two changes, CCache can now be used to implement both of
Varnish's grace and saint mode.

cache.go

@@ -35,33 +35,24 @@ func New(config *Configuration) *Cache {
 	return c
 }
 
-func (c *Cache) Get(key string) interface{} {
-	if item := c.get(key); item != nil {
-		return item.value
-	}
-	return nil
-}
-
-func (c *Cache) TrackingGet(key string) TrackedItem {
-	item := c.get(key)
-	if item == nil {
-		return NilTracked
-	}
-	item.track()
-	return item
-}
-
-func (c *Cache) get(key string) *Item {
+func (c *Cache) Get(key string) *Item {
 	bucket := c.bucket(key)
 	item := bucket.get(key)
 	if item == nil {
 		return nil
 	}
-	if item.expires < time.Now().Unix() {
-		c.deleteItem(bucket, item)
-		return nil
+	if item.expires > time.Now().Unix() {
+		c.conditionalPromote(item)
 	}
-	c.conditionalPromote(item)
+	return item
+}
+
+func (c *Cache) TrackingGet(key string) TrackedItem {
+	item := c.Get(key)
+	if item == nil {
+		return NilTracked
+	}
+	item.track()
 	return item
 }