HTTP2: moved docs into docs/ and make it markdown

lib/README.http2

@@ -1,99 +0,0 @@
-HTTP2 with libcurl
-
- Spec: http://www.rfc-editor.org/rfc/rfc7540.txt
-
- Document explaining it: http://daniel.haxx.se/http2/
-
- Build prerequisites
-  - nghttp2
-  - OpenSSL, NSS, GnutTLS or PolarSSL with a new enough version
-
- nghttp2 (https://github.com/tatsuhiro-t/nghttp2)
-
-  libcurl uses this 3rd party library for the low level protocol handling
-  parts. The reason for this is that HTTP/2 is much more complex at that layer
-  than HTTP/1.1 (which we implement on our own) and that nghttp2 is an already
-  existing and well functional library.
-
-  We require at least version 1.0.0.
-
- Over an http:// URL
-
-  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will
-  include an upgrade header in the initial request to the host to allow
-  upgrading to http2.
-
-  Possibly we can later introduce an option that will cause libcurl to fail if
-  not possible to upgrade. Possibly we introduce an option that makes libcurl
-  use http2 at once over http://
-
- Over an https:// URL
-
-  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will use
-  ALPN (or NPN) to negotiate which protocol to continue with. Possibly
-  introduce an option that will cause libcurl to fail if not possible to use
-  http2.  Consider options to explicitly disable ALPN and/or NPN.
-
-  ALPN is the TLS extension that http2 is expected to use. The NPN extension
-  is for a similar purpose, was made prior to ALPN and is used for SPDY so
-  early http2 servers are implemented using NPN before ALPN support is
-  widespread.
-
-SSL libs
-
-  The challenge is the ALPN and NPN support and all our different SSL
-  backends. You may need a fairly updated SSL library version for it to
-  provide the necessary TLS features. Right now we support:
-
-    OpenSSL:  ALPN and NPN
-    NSS:      ALPN and NPN
-    GnuTLS:   ALPN
-    PolarSSL: ALPN
-
-Multiplexing
-
-  Starting in 7.43.0, libcurl fully supports HTTP/2 multiplexing, which is the
-  term for doing multiple independent transfers over the same physical TCP
-  connection.
-
-  To take advantage of multiplexing, you need to use the multi interface and
-  set CURLMOPT_PIPELINING to CURLPIPE_MULTIPLEX. With that bit set, libcurl
-  will attempt to re-use existing HTTP/2 connections and just add a new stream
-  over that when doing subsequent parallel requests.
-
-  While libcurl sets up a connection to a HTTP server there is a period during
-  which it doesn't know if it can pipeline or do multiplexing and if you add
-  new transfers in that period, libcurl will default to start new connections
-  for those transfers. With the new option CURLOPT_PIPEWAIT (added in 7.43.0),
-  you can ask that a transfer should rather wait and see in case there's a
-  connection for the same host in progress that might end up being possible to
-  multiplex on. It favours keeping the number of connections low to the cost
-  of slightly longer time to first byte transfered.
-
-Applications
-
-  We hide http2's binary nature and convert received http2 traffic to headers
-  in HTTP 1.1 style. This allows applications to work unmodified.
-
-curl tool
-
-  curl offers the --http2 command line option to enable use of http2
-
-HTTP Alternative Services
-
-  Alt-Svc is a suggested extension with a corresponding frame (ALTSVC) in
-  http2 that tells the client about an alternative "route" to the same content
-  for the same origin server that you get the response from. A browser or
-  long-living client can use that hint to create a new connection
-  asynchronously.  For libcurl, we may introduce a way to bring such clues to
-  the applicaton and/or let a subsequent request use the alternate route
-  automatically. Spec:
-  http://tools.ietf.org/html/draft-ietf-httpbis-alt-svc-05
-
-TODO:
-
-  - Provide API to set priorities / dependencies of individual streams
-
-  - Implement "prior-knowledge" HTTP/2 connecitons over clear text so that
-    curl can connect with HTTP/2 at once without 1.1+Upgrade.
-