chore(package): remove browserify, tsify dev dependencies

both packages not used in the project anymore since we switched to webpack.
(tsify is a plugin for browserify)

fixes npm audit warnings for browserify

we probably missed this in #384 (adding browserify) and #394 (keeping tsify).

package.json

@@ -60,7 +60,6 @@
     "@types/chai": "^4.0.3",
     "@types/loglevel": "^1.4.29",
     "@types/mocha": "^5.2.3",
-    "browserify": ">=10.x",
     "chai": "^4.1.0",
     "clean-webpack-plugin": "^1.0.0",
     "cross-env": "^5.1.3",
@@ -88,7 +87,6 @@
     "npm-run-all": "^4.1.2",
     "pre-commit": "^1.2.2",
     "ts-loader": "^4.1.0",
-    "tsify": "^4.0.0",
     "tslint": "^5.8.0",
     "tslint-loader": "^3.5.3",
     "typedoc": "^0.13.0",