Merge pull request #84 from weshatheleopard/chartsheet_support

Issue #82: implementing all the nodes as documented in the OOXML standard
Version bump to 2.2.0
Regenerate gemspec for version 2.2.0
Moving towards the container object
Issue #83 progress
First take at the transparrent containers. Need a bit of polishing.
Issue #83: Transparent containers
Issue #83: Transparent containers
Cleanup vestigial code
Issue #83: Transparent containers
Issue #83: Transparent containers
Merge pull request #85 from weshatheleopard/transparent_containers

Transparent containers