package: install prettier and define linting scripts

This'll help to catch any errors in new code and keep their style consistent
While we're at it also uninstall unused `coffeelint` and remove files belonging to it

Author: fluvf

.coffeelintignore renamed to .prettierignore

@@ -0,0 +1,3 @@
+{
+  "singleQuote": true
+}

.prettierrc.json

@@ -8,6 +8,11 @@
   "engines": {
     "atom": "*"
   },
+  "scripts": {
+    "lint": "prettier --check .",
+    "lint:fix": "prettier --write .",
+    "test": "npm run lint && atom --test spec"
+  },
   "dependencies": {
     "async": "~0.2.6",
     "atom-select-list": "^0.7.0",
@@ -28,6 +33,6 @@
     }
   },
   "devDependencies": {
-    "coffeelint": "^1.9.7"
+    "prettier": "^2.1.2"
   }
 }