remove static/post.html from MANIFEST.in
remove Jinja2 dependency
replace abort(code) with proper exceptions and refactor request dispatch
cache PBKDF2 hash, closes #18

Markdown conversion is not the reason for 2s per 100 comments response,
the hash function is. When using the email/remote_addr from cache, the
response time is pretty fast.

* when uWSGI is available, use their caching framework

* for multi-threaded environment (the default), use a simple cache
  shipped with werkzeug
only create a reply box when needed

Previously this led to unnecessary object creation which impacted the
rendering time (on my machine 200 comments -> 1200ms) just to create
the postbox per comment (just the object initialization)).