fix: Handle absolute outputFile paths in Junit Reporter

Modifies the Junit Reporter so that it doesn't try to combine the output directory path and the output file, if the output file is already an absolute path

Closes #83

index.js

@@ -52,7 +52,9 @@ var JUnitReporter = function (baseReporterDecorator, config, logger, helper, for
   var writeXmlForBrowser = function (browser) {
     var safeBrowserName = browser.name.replace(/ /g, '_')
     var newOutputFile
-    if (outputFile != null) {
+    if (path.isAbsolute(outputFile)) {
+      newOutputFile = outputFile
+    } else if (outputFile != null) {
       var dir = useBrowserName ? path.join(outputDir, safeBrowserName)
                                : outputDir
       newOutputFile = path.join(dir, outputFile)