Add missing -r option from help command. Also add cmake a s a requirement in the README.

README.md

@@ -131,6 +131,7 @@ normal users will want to leave disabled as they can severely
 impact performance.
     
 ### Requirements
+* cmake
 * mbelib
 * sndfile
 

dsd_main.c

@@ -245,6 +245,7 @@ usage ()
   printf ("  -i <device>   Audio input device (default is /dev/audio)\n");
   printf ("  -o <device>   Audio output device (default is /dev/audio)\n");
   printf ("  -d <dir>      Create mbe data files, use this directory\n");
+  printf ("  -r <files>    Read/Play saved mbe data from file(s)\n");
   printf ("  -g <num>      Audio output gain (default = 0 = auto, disable = -1)\n");
   printf ("  -n            Do not send synthesized speech to audio output device\n");
   printf ("  -w <file>     Output synthesized speech to a .wav file\n");