Merge pull request #119 from UniversityofWarwick/category-filter

Category excluding filter.

lib/appenders/categoryFilter.js

@@ -0,0 +1,24 @@
+var levels = require('../levels');
+var log4js = require('../log4js');
+
+function contains(list, value) {
+    return list.indexOf(value) !== -1;
+}
+
+function categoryFilter (excludes, appender) {
+    if (typeof(excludes) === 'string') excludes = [excludes];
+    return function(logEvent) {
+        if (excludes.indexOf(logEvent.categoryName) === -1) {
+            appender(logEvent);
+        }
+    }
+}
+
+function configure(config) {
+    log4js.loadAppender(config.appender.type);
+    var appender = log4js.appenderMakers[config.appender.type](config.appender);
+    return categoryFilter(config.exclude, appender);
+}
+
+exports.appender = categoryFilter;
+exports.configure = configure;