Set extra duration to zero when ignoring rounding, this allows the us…

…er to generate an audiosprite without a gap. (#71)

audiosprite.js

@@ -159,6 +159,7 @@ module.exports = function(files) {
       if (opts.ignorerounding)
       {
         opts.logger.info('Ignoring nearest second silence gap rounding');
+        extraDuration = 0;
         delta = 0;
       }