Implement new memory check and an invert sort logical
Update the comments and help page
Change instances of invert to reverse
Move reverse variable to just before the scores are ranked
Change memory command to use sed to parse free memory.
Create new test which includes mem argument
Merge remote branch 'upstream/master' into rose-host-select-add-memory
Update help text to include units
Changes following review.
Remove None argument from printed threshold output
Merge pull request #829 from jmancell/rose-host-select-add-memory

rose host-select: add method to rank by free memory