tree: Improve wildcard conflict panic reason

Fixes #151

tree.go

diff --git a/tree.go b/tree.go
index b735534..ef9d564 100644
--- a/tree.go
+++ b/tree.go
@@ -144,16 +144,19 @@
 					numParams--
 
 					// Check if the wildcard matches
-					if len(path) >= len(n.path) && n.path == path[:len(n.path)] {
-						// check for longer wildcard, e.g. :name and :names
-						if len(n.path) >= len(path) || path[len(n.path)] == '/' {
-							continue walk
-						}
+					if len(path) >= len(n.path) && n.path == path[:len(n.path)] &&
+						// Check for longer wildcard, e.g. :name and :names
+						(len(n.path) >= len(path) || path[len(n.path)] == '/') {
+						continue walk
+					} else {
+						// Wildcard conflict
+						pathSeg := strings.SplitN(path, "/", 2)[0]
+						prefix := fullPath[:strings.Index(fullPath, pathSeg)] + n.path
+						panic("'" + pathSeg +
+							"' in new path '" + fullPath + "'" +
+							"' conflicts with existing wildcard '" + n.path +
+							"' in existing prefix '" + prefix + "'")
 					}
-
-					panic("path segment '" + path +
-						"' conflicts with existing wildcard '" + n.path +
-						"' in path '" + fullPath + "'")
 				}
 
 				c := path[0]