fixup: get tests working again

  - Blocked on tschaub/mock-fs#56 and
               broccolijs/broccoli-plugin#4

Author: caitp

filter.js

@@ -37,6 +37,7 @@ function Filter(inputTree, options) {
       this.outputEncoding = options.outputEncoding;
   }
 
+  this._debug = debugGenerator(this.description);
   this._cache = new Cache();
   this._canProcessCache = Object.create(null);
   this._destFilePathCache = Object.create(null);

test/test.js

@@ -7,6 +7,8 @@ var broccoliTestHelpers = require('broccoli-test-helpers');
 var makeTestHelper = broccoliTestHelpers.makeTestHelper;
 var cleanupBuilders = broccoliTestHelpers.cleanupBuilders;
 
+require('broccoli-plugin').initialize();
+
 var inherits = require('util').inherits;
 var _mockfs = require('mock-fs');
 var fs = require('fs');