Update 19 Guests with less than X MB free.ps1

Added option to disregard small disks. Default set to not check disks less than 1024 MB as these will always pop in the original report. Checking if a disk that is less than 1024 MB has less free space than 1024 MB seems redundant.
Merge pull request #60 from jones-g/patch-3

Update 19 Guests with less than X MB free.ps1