fix: use output dir per reporter

Closes #42

Author: kombucha

lib/reporter.js

@@ -116,7 +116,8 @@ var CoverageReporter = function(rootConfig, helper, logger) {
         var collector = collectors[browser.id];
         if (collector) {
           pendingFileWritings++;
-          var out = path.resolve(outDir, browser.name);
+          var reporterOutDir = helper.isDefined(reporterConfig.dir) ? helper.normalizeWinPath(path.resolve(basePath, reporterConfig.dir)) : outDir,
+              out = path.resolve(reporterOutDir, browser.name);
           helper.mkdirIfNotExists(out, function() {
             log.debug('Writing coverage to %s', out);
             var options = helper.merge({}, reporterConfig, {