refactor: Removed Promise Polyfill to reduce bundle size (#417)

Summary:

Removed Promise Polyfill from browser entry point to reduce bundle size. A user can still use the SDK in older browsers by including the promise polyfill themselves.

Test plan:
All tests pass by providing promise polyfill as part of the test setup.

packages/optimizely-sdk/karma.bs.conf.js

@@ -26,6 +26,9 @@ module.exports = function(config) {
     logLevel: config.LOG_INFO,
 
     // list of files / patterns to load in the browser
-    files: ['./lib/index.browser.tests.js'],
+    files: [
+      './node_modules/promise-polyfill/dist/polyfill.min.js',
+      './lib/index.browser.tests.js'
+    ],
   });
 };

packages/optimizely-sdk/karma.umd.conf.js

@@ -26,6 +26,10 @@ module.exports = function(config) {
     logLevel: config.LOG_INFO,
 
     // list of files / patterns to load in the browser
-    files: ['./dist/optimizely.browser.umd.min.js', './lib/index.browser.umdtests.js'],
+    files: [
+      './node_modules/promise-polyfill/dist/polyfill.min.js',
+      './dist/optimizely.browser.umd.min.js',
+      './lib/index.browser.umdtests.js'
+    ],
   });
 };

packages/optimizely-sdk/lib/index.browser.js

@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-require('promise-polyfill/dist/polyfill');
 var logging = require('@optimizely/js-sdk-logging');
 var fns = require('./utils/fns');
 var configValidator = require('./utils/config_validator');

packages/optimizely-sdk/package.json

@@ -39,7 +39,6 @@
     "@optimizely/js-sdk-utils": "^0.2.0",
     "json-schema": "^0.2.3",
     "murmurhash": "0.0.2",
-    "promise-polyfill": "8.1.0",
     "uuid": "^3.3.2"
   },
   "devDependencies": {
@@ -62,6 +61,7 @@
     "sinon": "^2.3.1",
     "webpack": "^4.25.1",
     "webpack-cli": "^3.1.2",
+    "promise-polyfill": "8.1.0",
     "lodash": "^4.17.11"
   },
   "publishConfig": {