Merge pull request #129 from jonschlinkert/master

housekeeping update, docs, description, code comments.
adding categories to root context
build
adding category examples and building
making sure the current page context values of tags and categories don't override the root context values of tags and categories
building
bumping version and updating readme
reworking the layout logic
building
adding a layout2 for testing
updating a couple of pages to use a different layout
building
moving when tags and categories are added to the page context
building
fixing version and updating readme