- what happens if content-type ends up incorrect?
- teach ext to do syntax highlighting
- production-readiness
  - benchmark with ab / h2load
  - consider behavior under resource exhastion
  - what kind of resource limits need to be considered?
  - handling too many open file handles
  - handling too many connections
  - preventing oom
  - stress testing
  - add structopt-toml support
  - test conformance with h2spec / (what about http 1?)
  - handle more request / response headers
  - use more status codes
  - deal with accept request header
  - accept / content-type
  - content-type charsets
  - etag and header method?
- make_error_response should find io errors to any recursive depth
- make plain path links, [index.html], work
- rst support
- add a way to explicitly request an index listing
- markdown
  - display README.md for dirs by default
  - strip -- comments from top of md files
  - with -x, check missing .html files for .md instead
- make errors semantic
- make errors carry URLs
- async is_dir
- add context to errors
- prevent responding files outside of root_dir
- catch and report panic
- error on binding bound socket / port