Rework builds

This allows users to import only the history they need instead of
relying on tree-shaking to get rid of code they don't. It also adds
singleton instances to both browser and hash history, which makes sense
since the library runs in the context of a single web page.

.gitignore

@@ -1,3 +1,4 @@
 /build/
 /fixtures/*/history.js
-/node_modules/
+
+node_modules/

.travis.yml

@@ -14,9 +14,11 @@ jobs:
     script: echo "Releasing $TRAVIS_TAG to npm with tag \"$NPM_TAG\" ..."
     deploy:
       provider: npm
-      skip_cleanup: true
-      tag: "$NPM_TAG"
+      edge: true
+      cleanup: false
       email: [email protected]
-      api_key: "$NPM_TOKEN"
+      api_token: "$NPM_TOKEN"
+      src: "build/history"
+      tag: "$NPM_TAG"
       on:
         tags: true

karma.conf.js

@@ -78,13 +78,20 @@ module.exports = function(config) {
           {
             test: /\.js$/,
             exclude: /node_modules/,
-            loader: 'babel-loader'
+            loader: 'babel-loader',
+            options: {
+              presets: [['@babel/preset-env', { loose: true }]],
+              plugins: ['babel-plugin-dev-expression']
+            }
           }
         ]
       },
       resolve: {
         alias: {
-          history$: path.resolve(__dirname, 'modules/index.js')
+          history$: path.resolve(
+            __dirname,
+            'packages/history/modules/history.js'
+          )
         }
       },
       plugins: [