disallowing --watch and --join together for the time being.

lib/command.js

@@ -83,7 +83,7 @@
                   return compileScript(source, code.toString(), base);
                 }
               });
-              if (opts.watch) {
+              if (opts.watch && !opts.join) {
                 return watch(source, base);
               }
             }

src/command.coffee

@@ -89,7 +89,7 @@ compileScripts = ->
                 compileJoin() if helpers.compact(contents).length is sources.length
               else
                 compileScript(source, code.toString(), base)
-            watch source, base if opts.watch
+            watch source, base if opts.watch and not opts.join
     compile source, true
 
 # Compile a single source script, containing the given code, according to the