Refactored AsciidoctorTask so that most properties can now be set either via property assignment or more flexible method calls. For #120
Fixed issues with legacy attribute formats embedded inside options. For #120.
Updated README for #120
Updated README for #120 to place backwards compatibility notes regarding options and attributes in correct location
Merge pull request #121 from ysb33r/development

Addressing #120 (Suggestions for refactoring)