build(broccoli): add testing infrastructure for our build plugins

components:
- gulp test.unit.broccoli task
- mock-fs for mocking our FS in unit tests
- jasmine d.ts file for type checking

jasmine lib is provided by minijasmine2 so we don't need to include it explicitly

tools/tsd.json

@@ -13,6 +13,9 @@
     },
     "es6-promise/es6-promise.d.ts": {
       "commit": "d5f92f93bdb49f332fa662ff1d0cc8700f02e4dc"
+    },
+    "jasmine/jasmine.d.ts": {
+      "commit": "055b3172e8eb374a75826710c4d08677872620d3"
     }
   }
 }