experiment with generating XML object bindings
add TextFrame.add_paragraph and .vertical_anchor

* add TextFrame.add_paragraph()
* add TextFrame.vertical_anchor setter only
* add constants module for MSO.* symbolic constants
* add bullet-slide example in user documentation
add .font.size and .bold to Run and Paragraph

* add schema page for CT_TextParagraph
* bring user documentation up to date
* add pptx.presentation._Font class with .size and .bold properties
* add .font property to Run and Paragraph
* refactor pptx.presentation class-local __nsmap to module-level _nsmap
* refactor qname to qtag
prepare v0.2.0 release

* revamp docs home page and README.rst
* Add example for shapes.add_picture()
* Add example for shapes.add_textbox()
* add pull version string into setup.py from pptx/__init__.py