added ts dir to clean

Author: Kevin Groat

package.json

@@ -19,7 +19,7 @@
     "build_file": "dist/testdouble.js"
   },
   "scripts": {
-    "clean": "rimraf dist lib coverage",
+    "clean": "rimraf dist lib coverage ts",
     "postclean": "mkdirp dist",
     "compile:browser": "cross-conf-env browserify src/index.ts --standalone td --outfile $npm_package_config_build_file -p tsify -p headerify",
     "compile:node": "tsc --project ./tsconfig.node.json",