Remove singleton patterns collection

This should be up to the caller, who can decide if they might want to
reload the patterns list later, or have multiple collections with different
default patterns.

lib/index.js

@@ -189,29 +189,26 @@ function GrokCollection() {
     };
 }
 
-var defaultPatterns;
 var patternsDir = __dirname + '/patterns/';
 
 function doLoadDefault(loadModules) {
-    if (!defaultPatterns) {
-        defaultPatterns = new GrokCollection();
-        var files = fs.readdirSync(patternsDir);
-        if (files && files.length) {
-            files.filter(function(file) {
-                return !loadModules || !loadModules.length || loadModules.indexOf(file) !== -1;
-            }).forEach(function (file) {
-                defaultPatterns.loadSync(patternsDir + file);
-            })
-        }
+    var result = new GrokCollection();
+
+    var files = fs.readdirSync(patternsDir);
+    if (files && files.length) {
+        files.filter(function(file) {
+            return !loadModules || !loadModules.length || loadModules.indexOf(file) !== -1;
+        }).forEach(function (file) {
+            result.loadSync(patternsDir + file);
+        })
     }
 
-    return defaultPatterns;
+    return result;
 }
 
 module.exports = {
     loadDefault: function (callback, loadModules) {
-        doLoadDefault(loadModules);
-        callback(defaultPatterns);
+        callback(doLoadDefault(loadModules));
     },
 
     loadDefaultSync: doLoadDefault,