templating: Make blog archives generator expose more templating data. In addition to pagination data, also expose a non-paginating iterator that lists all posts in a source by chronological order.

cov-core==1.15.0
coverage==4.0.3
invoke==0.12.2
mock==1.0.1
pytest==2.8.7
pytest-cov==2.2.1
pytest-mock==0.10.1