Revert "Bump tsd from 0.12.1 to 0.20.0 (#366)"

This reverts commit e1b85bd.

Author: Marius

package.json

@@ -72,7 +72,7 @@
     "regenerator-runtime": "^0.13.5",
     "temp": "^0.9.4",
     "throttle": "^1.0.3",
-    "tsd": "0.20.0",
+    "tsd": "0.12.1",
     "uglify-js": "^3.9.2"
   },
   "dependencies": {