fix(appveyor): limit concurrency to 5, to prevent reach the resource limit in appveyor?

package.json

@@ -36,7 +36,7 @@
     "test:phantomjs": "cross-env LC_ALL=C WECHATY_HEAD=phantomjs ava --verbose --fail-fast --serial --timeout=5m \"dist/{src,test}/**/*.spec.js\"",
     "test:chrome": "cross-env LC_ALL=C WECHATY_HEAD=chrome ava --serial --fail-fast --verbose --timeout=5m \"dist/{src,test}/**/*.spec.js\"",
     "test:bug": "cross-env LC_ALL=C WECHATY_HEAD=chrome WECHATY_LOG=silly ava --serial --fail-fast --verbose --timeout=5m \"dist/src/message.spec.js\"",
-    "test:chrome:fast": "cross-env LC_ALL=C WECHATY_HEAD=chrome ava --fail-fast --timeout=5m \"dist/{src,test}/**/*.spec.js\"",
+    "test:chrome:fast": "cross-env LC_ALL=C WECHATY_HEAD=chrome ava --concurrency 5 --fail-fast --timeout=5m \"dist/{src,test}/**/*.spec.js\"",
     "testdev": "cross-env LC_ALL=C WECHATY_LOG=silly ava --ext ts --serial --verbose --fail-fast --timeout=2m",
     "testdist": "cross-env WECHATY_LOG=SILLY WECHATY_HEAD=chrome ava --ext ts --verbose --fail-fast --timeout=2m",
     "test:pack": "npm run dist && rm -fr package wechaty-*.*.*.tgz && npm pack --verbose  && tar zxvf wechaty-*.*.*.tgz",
@@ -106,8 +106,6 @@
     "node": ">= 6.9.0"
   },
   "dependencies": {
-    "@types/selenium-webdriver": "3.0.4",
-    "@types/socket.io": "1.4.29",
     "bl": "1.2.1",
     "body-parser": "1.17.2",
     "brolog": "1.1.18",
@@ -115,7 +113,6 @@
     "express": "4.15.2",
     "is-ci": "1.0.10",
     "is-docker": "1.1.0",
-    "moment": "2.18.1",
     "ps-tree": "1.1.0",
     "request": "2.81.0",
     "retry-promise": "1.0.0",
@@ -131,7 +128,9 @@
     "@types/mime": "0.0.29",
     "@types/node": "7.0.19",
     "@types/request": "0.0.43",
+    "@types/selenium-webdriver": "3.0.4",
     "@types/sinon": "2.2.2",
+    "@types/socket.io": "1.4.29",
     "@types/ws": "0.0.41",
     "apiai": "4.0.2",
     "ava": "0.18.2",