feat: allow multiple report types

This change refactors the way the coverageReporter configuration
works by adding a new 'reporters' property.  This property is a list
of configurations for any reporters that should be used.  This allows
the user to ask for multiple output types at the same time.

For example:

coverageReporter: {
    dir : 'coverage/',
    reporters: [{
      type: 'html'
    }, {
      type: 'text'
    }, {
        type: 'cobertura'
    }]
}

This configuration outputs reports in html, text, and cobertura
from the same run of karma.

Note: the code is designed to be backwards compatible with the older
method of specifying the options.

SQUASH: format feature

lib/reporter.js

@@ -42,7 +42,11 @@ var CoverageReporter = function(rootConfig, emitter, helper, logger) {
   var config = rootConfig.coverageReporter;
   var basePath = rootConfig.basePath;
   var outDir = config.dir;
-  var type = config.type;
+  var reporters = config.reporters;
+
+  if (!helper.isDefined(reporters)) {
+    reporters = [config];
+  }
 
   this.adapters = [];
   var collectors;
@@ -51,6 +55,10 @@ var CoverageReporter = function(rootConfig, emitter, helper, logger) {
 
   function writeEnd() {
     if (!--pendingFileWritings) {
+      // cleanup collectors
+      Object.keys(collectors).forEach(function(key) {
+         collectors[key].dispose();
+      });
       fileWritingFinished();
     }
   }
@@ -93,28 +101,30 @@ var CoverageReporter = function(rootConfig, emitter, helper, logger) {
   };
 
   this.onRunComplete = function(browsers, results) {
-    browsers.forEach(function(browser) {
-      var collector = collectors[browser.id];
-      if (collector) {
-        pendingFileWritings++;
-        var out = path.resolve(outDir, browser.name);
-        helper.mkdirIfNotExists(out, function() {
-          var options = helper.merge({}, config, {
-            dir : out,
-            sourceStore : new BasePathStore({
-              basePath : basePath
-            })
+    reporters.forEach(function(reporterConfig) {
+      browsers.forEach(function(browser) {
+        var collector = collectors[browser.id];
+        if (collector) {
+          pendingFileWritings++;
+          var out = path.resolve(outDir, browser.name);
+          helper.mkdirIfNotExists(out, function() {
+            var options = helper.merge({}, reporterConfig, {
+              dir : out,
+              sourceStore : new BasePathStore({
+                basePath : basePath
+              })
+            });
+            var reporter = istanbul.Report.create(reporterConfig.type, options);
+            try {
+              reporter.writeReport(collector, true);
+            } catch (e) {
+              log.error(e);
+            }
+            collector.dispose();
+            writeEnd();
           });
-          var reporter = istanbul.Report.create(type, options);
-          try {
-            reporter.writeReport(collector, true);
-          } catch (e) {
-            log.error(e);
-          }
-          collector.dispose();
-          writeEnd();
-        });
-      }
+        }
+      });
     });
   };