fix: remove positioning sourcemap from umd build

Closes #66

package.json

@@ -88,6 +88,7 @@
     "sass-loader": "~4.0.1",
     "sinon": "~1.17.4",
     "sinon-chai": "~2.8.0",
+    "source-map-loader": "~0.1.5",
     "sourcemap-istanbul-instrumenter-loader": "~0.2.0",
     "standard-version": "~2.4.0",
     "style-loader": "~0.13.0",

webpack.config.umd.ts

@@ -66,6 +66,10 @@ module.exports = {
       test: /\.ts$/,
       loader: 'tslint-loader?emitErrors=true&failOnHint=true',
       exclude: /node_modules/
+    }, {
+      enforce: 'pre',
+      test: /ng\-bootstrap\/util\/positioning/,
+      loader: 'source-map-loader'
     }, {
       test: /\.ts$/,
       loader: 'awesome-typescript-loader',