Prefer initializing coffee variables after declaration

This stems from a discussion about the following piece of code.

```coffee
describe 'ChallengesController', ->
  challenge=
  response=
```

Here we declare two variables, `challenge` and `response`, but don't initialize them (effectively giving them a value of `undefined`). These unbalanced expressions didn't sit well with a part of the team, so prefer to always initialize variables after declaring them.