Some refactoring to support individual test cases
Updates to the README and project template
Added file-fix-it example
Modified TestCase to use STDOUT or a supplied output IO for printing results
Run test cases in parallel if --parallel option is set
Refactored TestCase#puts_with_case to use one print

This is because printing in parallel might break up messages if they
are printed across multiple calls to print
Set the parallel option if a process count is given
Updated README with info on parallel processing