Issue #87: Moving Writer functionality to OOXMLTopLevelObject
Issue #87: Moving Writer functionality to OOXMLTopLevelObject
Merge branch 'master' of github.com:weshatheleopard/rubyXL into moving_writers

Conflicts:
	lib/rubyXL/workbook.rb
Issue #87: Moving Writer functionality to OOXMLTopLevelObject
Dependencies, comments
Merge branch 'master' of github.com:weshatheleopard/rubyXL into moving_writers
Merge branch 'master' of github.com:weshatheleopard/rubyXL into moving_writers
Issue #87: moving ContentTypes
A bit of cleanup since that code is about to go away
Issue #88: handling mc:AlternateContent node in Workbook; adding more core properties.
Merge branch 'master' of github.com:weshatheleopard/rubyXL into moving_writers
Issue #87: Moving ThemeWriter to OOXMLObject
Issue #87: Moving writer functionality into OOXMLTopLevelObject
Cleaning up some comments
Version bump to 2.4.0
Regenerate gemspec for version 2.4.0