Rule: one-var

The `one-var` rule disallows multiple variable declarations per function scope.

```js
function foo() {
  var bar;
  var baz;
}
```

See: http://jslinterrors.com/combine-this-with-the-previous-var-statement/

In addition, I removed an unnecessary test that was erroring (I believe it was introduced when two conflicting PRs were merged.)