docs_app: Switch docs app to Jinja2 templates

They're a bit more powerful.

Specifically, we can use a loader to make specifying template paths cleaner.
Also, we can choose to escape or not escape markup with the |e tag filter.

This allows us to embed the simple push example in both code and live form.
Merge pull request #11 from AdrenalineBrowser/docsapp_use_jinja2

docs_app: Switch docs app to Jinja2 templates
Merge branch 'master' of github.com:AdrenalineBrowser/dopamine into ios_push
Added iOS push handling

This patch includes functionality for accessing the iOS web push
mechanism.  It includes a general path for interacting with the
browser from javascript, code for detecting Adrenaline on iOS, and
simple handling web push.