Remove module number

The number is actually a test number so it should be name appropriately.
qUnit's module is not really shown or nested as a separate identity from
the test. If I want the qUnit's module number, I will need to calculate
it.
Change var name from module to test

In _readResults, we're really working with each test shown to user. The
concept of module hierarchy only exists in the source code but not
display clearly. Renaming variable to tests would be best. As mentioned
in previous commit, if we want info about module, it will need to be
computed. Will create new methods for handling those in the future.
Change if to check for valid instead of invalid

Change the if logic to check whether a test has "pass" or "fail" before
performing action, instead of checking if it doesn't and skip action.
This reduce the line of code and make it a little easier to read.
Refactor _readResults

Remove lastNewModule index. It's only reference once and could be
calculated from the array length so there's not much point to it.
Create a new previousModule to to make the code less word-y when
referencing the previous module, instead of accessing from the array.