change 'then' command to 'past' and 'future'

bin/dogapi

@@ -15,7 +15,8 @@ var usage = [
     "  dogapi <command> --help",
     "  dogapi --version",
     "  dogapi now",
-    "  dogapi then <seconds-ago>"
+    "  dogapi past <seconds-ago>",
+    "  dogapi future <seconds-ahead>"
 ];
 var help = [];
 for(var key in dogapi){
@@ -47,8 +48,10 @@ if(command === "servicecheck"){
 
 if(command === "now"){
     console.log(dogapi.now());
-} else if(command === "then" && args._.length > 3){
+} else if(command === "past" && args._.length > 3){
     console.log(dogapi.now() - parseInt(args._[args._.length - 1]));
+} else if(command === "future" && args._.length > 3){
+    console.log(dogapi.now() + parseInt(args._[args._.length - 1]));
 } else if(dogapi.hasOwnProperty(command)){
     if(subcommand){
         dogapi[command].handleCli(subcommand, args, function(err, res){