Moving Get-RoboCopyArguments to an inner function

When running the completer for robocopy, $error fills up with messages
about not finding Get-RoboCopyArguments.
This seems to fix it
Update ArgumentCompleterFunction.snippets.ps1xml

Fixing spelling error
Making new-completionresult accept more than one item from the pipeline
Merge pull request #23 from powercode/master

Moving Get-RoboCopyArguments to an inner function