fix(package): update execa to version 2.0.4

Closes #95

Author: greenkeeper[bot]

package.json

@@ -54,7 +54,7 @@
     "can-view-parser": "^4.0.2",
     "deep-assign": "^3.0.0",
     "disparity": "^2.0.0",
-    "execa": "^0.9.0",
+    "execa": "^2.0.4",
     "fs-extra": "^5.0.0",
     "globby": "^7.1.1",
     "is-git-clean": "^1.1.0",