TBR: Add tap-xunit dev dependency.

Change-Id: Ibbcbd3da48a7c9c2be7e6f12ae77fa7663ec38bd
diff --git a/package.json b/package.json
index 05622ef..397ea95 100644
--- a/package.json
+++ b/package.json
@@ -17,6 +17,7 @@
     "prova": "aghassemi/prova#0.0.4",
     "run-parallel": "~1.1.1",
     "stream-to-array": "~2.0.2",
+    "tap-xunit": "~1.1.1",
     "which": "~1.1.1",
     "xtend": "~4.0.0"
   },