Fix #30 Fix #31 use <mtime> instead of <ctime> which is more relevant

Also means we can use <touch> to force a file to rebuild, since touch changes <mtime>

src/input/metadata.js

@@ -36,7 +36,7 @@ exports.update = function(opts, callback) {
       next(null, {
         absolute: absolute,
         relative: filePath,
-        fileDate: Math.max(stats.ctime.getTime(), stats.mtime.getTime())
+        fileDate: stats.mtime.getTime()
       });
     });
   }

src/utils/make.js

@@ -16,7 +16,7 @@ exports.exec = function(input, output, metadata, options, callback) {
   });
   var process = tasks.filter(function(task) {
     try {
-      var destDate = fs.statSync(task.dest).ctime.getTime();
+      var destDate = fs.statSync(task.dest).mtime.getTime();
       return task.metadata.fileDate > destDate;
     } catch (ex) {
       return true;