conn alias for lwt servers
create constructor for lwt servers
rename create -> make
Server.t should be abstract in the lwt backend
simplify conn_closed callback
renovate opam file using 1.2 features

* add various metadata
* set build/test for deps
* add build-{test,doc} commands
fixup respond_error in lwt

* take headers optionally
* default status
Merge branch 'rgrinberg-simplify_lwt_server'
Merge branch 'rgrinberg-opam_1_2'
Bump to 0.14.0 and sync CHANGES
Use bytes to start migrating to `-safe-string`
Remove the `Cohttp.Base64` module in favour of the external `base64`

(which is now a new dependency)
Internal rearrangement: move `cohttp` subdir to `lib`

This is just for consistency with most other libraries, since we
no longer use obuild which was why this differed in the first place
regen oasis
Fix Base64 in oasis file
More info in CHANGES about the #210 changes
add pull req numbers in CHANGES
Flush the response body to the network by default, rather than
buffering by default.  The `?flush` optional parameter can still
be explicitly set to false if flushing is not desired

Fixes #205