Fix compilation errors in some classes
Added conversion support for some css properties

Properties:
- font (adding first in a list of fonts separated by commas);
- font-size support for px;
- background-color property for run and paragraph properties;
- added strike css property as "[line-through]";
- enabled vertical alignment and added "sub" to be checked;
Merge pull request #68 from ai-github/master

Added conversion support for some css properties (convert from xhtml to docx).