Fixing loop when creating issue with no parent

* This fixes an issue where hitting enter when prompted for the parent
  issue ID without specifying a number entered an endless loop. This
  was due to parseInt(answer) resulting to NaN which apparently is less
  then zero.
* The resolution I chose was to check whether the parseInt(answer) > 0
  _or_ whether the answer === false. Either one is a valid answer and
  will get the user into the correct code path.
Merge pull request #4 from guywithcrookedface/add_parent

Fixing loop when creating issue with no parent