💄 Tighten lint rules

coffeelint.json had some rules set to ignore, but since #3116 was merged there
are no violations of these rules in the code anymore. Tighten up the rules to
prevent those kinds of errors from creeping back in.

Test Plan:

Lint executes without finding any errors

```
$ ./script/grunt coffeelint
Running "coffeelint:src" (coffeelint) task
>> 80 files lint free.

Running "coffeelint:build" (coffeelint) task
>> 23 files lint free.

Running "coffeelint:test" (coffeelint) task
>> 40 files lint free.
Done, without errors.
```

coffeelint.json

@@ -1,14 +1,8 @@
 {
-  "indentation": {
-    "level": "ignore"
-  },
   "max_line_length": {
     "level": "ignore"
   },
   "no_empty_param_list": {
     "level": "error"
-  },
-  "no_unnecessary_fat_arrows": {
-    "level": "ignore"
   }
 }