build(npm): use git in reinstall

  Switches from rimraf to git to clean project
    - this still respects dot files

package.json

@@ -11,6 +11,7 @@
     "build": "ng build",
     "dartanalyzer": "cd dist/dart && pub install && cd ../.. && ts-node scripts/ci/dart_analyzer",
     "demo-app": "cd src && ng serve",
+    "reinstall": "git clean -dfx -e '.*'",
     "test": "karma start test/karma.conf.js",
     "tslint" : "tslint -c tslint.json 'src/**/*.ts'",
     "typings": "typings install --ambient"