http2: significant internal refactoring

* tighten up the Http2Stream/Http2Session lifecycle, destroy, and
  error handling. Some simplification, and more new tests

* Eliminate queuing of internal callbacks. Queuing these to fire on
  the next event loop tick was throwing off timing. Now the js callbacks
  are called directly as they happen. This will require a bit more
  finesse on the javascript side (to ensure appropiate timing of
  destroy/shutdown actions) but that is handled from within the core
  api impl so users should not be affected.

* fix debug output with nghttp2

PR-URL: nodejs#138
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: jasnell

deps/nghttp2/nghttp2.gyp

@@ -24,12 +24,14 @@
         'lib/nghttp2_buf.h',
         'lib/nghttp2_callbacks.c',
         'lib/nghttp2_callbacks.h',
+        'lib/nghttp2_debug.c',
+        'lib/nghttp2_debug.h',
         'lib/nghttp2_frame.c',
         'lib/nghttp2_frame.h',
         'lib/nghttp2_hd.c',
         'lib/nghttp2_hd.h',
-        'lib/nghttp2_hd_huffman_data.c',
         'lib/nghttp2_hd_huffman.c',
+        'lib/nghttp2_hd_huffman_data.c',
         'lib/nghttp2_hd_huffman.h',
         'lib/nghttp2_helper.c',
         'lib/nghttp2_helper.h',