Add a few comments.

ptyhelper.c

@@ -1,3 +1,9 @@
+/*
+ * ptyhelper: a utility that runs a command in a pseudoterm and then streams
+ * stdio to/from it.  Intended to get around the node.js loss of C/UNIX 
+ * functionality.
+ * Remember to compile with -lutil.
+ */
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>