Unref our inmemory-cache expiration timer so that it doesn't hold the…

… process open (issue #68).

lib/passport-saml/inmemory-cache-provider.js

@@ -13,7 +13,6 @@
  * @constructor
  */
 var CacheProvider = function (options) {
-
     var self = this;
     this.cacheKeys = {};
 
@@ -28,8 +27,7 @@ var CacheProvider = function (options) {
     this.options = options;
 
     // Expire old cache keys
-    setInterval(function(){
-
+    var expirationTimer = setInterval(function(){
         var nowMs = new Date().getTime();
         var keys = Object.keys(self.cacheKeys);
         keys.forEach(function(key){
@@ -39,6 +37,10 @@ var CacheProvider = function (options) {
         });
     }, this.options.keyExpirationPeriodMs);
 
+    // we only want this to run if the process is still open; it shouldn't hold the process open (issue #68)
+    //   (unref only introduced in node 0.9, so check whether we have it)
+    if (expirationTimer.unref)
+        expirationTimer.unref();
 };