Merge pull request #30 from IanJRigg/master

got it
Merge pull request #31 from IanJRigg/master

getting most recent code
Merge pull request #32 from IanJRigg/master

Pulling files to Chris' branch
Merge pull request #33 from IanJRigg/master

updating
added validate_operand method
Merge pull request #89 from candaya/master

adding validate_operands