Refactor hoisted and locally-redeclarated variables

[michaelsanford]

The err variable declared in lib/runner.js:137 will be overwritten by the one in :153 because those variables live in the same scope.

To mitigate this problem, I avoided creating a variable at all and refactored by inlining the object into the call to emit(), which is no less readable and slightly more efficient (avoids a variable assignment).

Sort of similarly, we can't re-scope a named parameter with var, as in lib/debug-helper.js:9. That line could be improved (and made slightly safer) by being changed to:

module.exports = function (logger) {
  // other code
  logger = typeof logger !== 'undefined' ? logger : console;`
  // other code
}

[michaelsanford]

After looking at it again, it is actually inefficient to emit directly. To avoid hoisting and reassignment, I've split the errors into two variables.