This release adds the the Stencil class to the C++ module (see #10). Along with stencils there is a basic Context class called Context::Map against which stencils can be rendered (it is mainly useful for testing stencil rendering, see for example the stencil tests). We still need to implement Python and R contexts for stencils to be really useful but this release provides important foundations for doing that.
In support of stencils, this release adds useful utilities to the C++ module: xml and html document classes (thanks, respectively, to pugixml and tidy-html5). The Stencil class is derived from Xml::Document and adding CSS selectors to the Xml::Node class has allowed us to add some powerful and concise rendering features to stencils.