chore(project): bump devDependency versions

Addresses the most urgent <npm audit> issues.

package.json

@@ -51,8 +51,8 @@
     "eslint-plugin-bpmn-io": "^0.5.2",
     "execa": "^0.8.0",
     "jsondiffpatch": "^0.1.26",
-    "karma": "^1.7.0",
-    "karma-browserify": "^5.2.0",
+    "karma": "^2.0.2",
+    "karma-browserify": "^5.3.0",
     "karma-chrome-launcher": "^2.1.1",
     "karma-env-preprocessor": "^0.1.1",
     "karma-firefox-launcher": "^1.0.1",
@@ -63,7 +63,7 @@
     "karma-sinon-chai": "^1.3.2",
     "karma-spec-reporter": "0.0.31",
     "mkdirp": "^0.5.1",
-    "mocha": "^4.0.1",
+    "mocha": "^5.2.0",
     "mocha-test-container-support": "0.2.0",
     "npm-run-all": "^4.1.2",
     "phantomjs-prebuilt": "^2.1.12",