Removed appendNode() from Peach_Markup_Comment

- Integrated with append()
Added getOriginal() for BreakControlWrapper
Implemented tests for Peach_Markup_Text
Fixed Exception type

- Exception => InvalidArgumentException
Implemented tests for Peach_Markup_EmptyElement

- Applied implementation of Peach_Markup_ElementTest
Modified setter methods of DefaultBuilder

- TODO: tests incompleted.
Implemented tests for Peach_Markup_Code
Added echoMode support
Implemented tests for Context classes

Others:

- Removed CDATA section support
Added getBuilder() and setBuilder()
Added some methods for Peach_Markup_Html

Others:

- Enriched PHPDoc comments
Implemented tests for Peach_Markup_DefaultBreakControl