lint before test. (#3147)

Also turn on lint cacheing to make this change painless ;)
add lint cache to gitignore...

Author: Arthur Cinader

.gitignore

@@ -44,6 +44,7 @@ lib/
 
 # cache folder
 .cache
+.eslintcache
 
 # Mac DS_Store files
 .DS_Store

package.json

@@ -67,8 +67,9 @@
   },
   "scripts": {
     "dev": "npm run build && node bin/dev",
-    "lint": "eslint ./",
+    "lint": "eslint --cache ./",
     "build": "babel src/ -d lib/",
+    "pretest": "npm run lint",
     "test": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=3.2.6} MONGODB_STORAGE_ENGINE=mmapv1 NODE_ENV=test TESTING=1 $COVERAGE_OPTION jasmine",
     "test:win": "cross-env MONGODB_VERSION=${MONGODB_VERSION:=3.2.6} MONGODB_STORAGE_ENGINE=mmapv1 NODE_ENV=test TESTING=1 jasmine",
     "coverage": "cross-env COVERAGE_OPTION='./node_modules/.bin/istanbul cover' npm test",