prepare for 0.19

prepare for 0.18

prepare for 0.17

prepare for 0.16

prepare for 0.15

Release 0.14

CHANGES:

- breaking: `set_top_handler` takes a stream request, for more generality

- Don't let client handling threads handle SIGINT/SIGHUP
- improve termination behavior (wait for threads to terminate when shutting down server)
- Preserve client address down to Request.t
- add `Tiny_httpd_io` module, abstraction over IOs (output/input) as better IO channels
    than the stdlib's
- add `Tiny_httpd_html.to_writer`
- add `IO.Writer.t`, a push based stream.
- add `Server.run_exn`
- add `Tiny_httpd_pool`
- server: add `IO_BACKEND` abstraction; implement a unix version of it

- perf: use TCP_NODELAY for client sockets
- perf: use a resource pool to recycle buffers, improves memory consumption and GC pressure

prepare for 0.13

prepare for 0.12

fix tests on non-linux

prepare for 0.10