Use // to start comment instead of #.

Fixes #189.

R=r
CC=rsc
https://golang.org/cl/155055

doc/go_spec.html

@@ -4190,10 +4190,10 @@ buffered channels:
 </p>
 
 <pre>
-s := make([]int, 10, 100);        # slice with len(s) == 10, cap(s) == 100
-s := make([]int, 10);             # slice with len(s) == cap(s) == 10
-c := make(chan int, 10);          # channel with a buffer size of 10
-m := make(map[string] int, 100);  # map with initial space for 100 elements
+s := make([]int, 10, 100);        // slice with len(s) == 10, cap(s) == 100
+s := make([]int, 10);             // slice with len(s) == cap(s) == 10
+c := make(chan int, 10);          // channel with a buffer size of 10
+m := make(map[string] int, 100);  // map with initial space for 100 elements
 </pre>