fixed runtime error in RST_STREAM
Implemented Flow Control

* decoder/encoder for WINDOW_UPDATE frame
* Connection changes:
    + fcw_send/fcw_recv counters for stream/connection structures
    + allow WINDOW_UPDATE frames on closed connection (ignore them)
    + split send() method to send_headers() and send_data()
    + send_blocked() - send blocked data
    + fcw_update() - increase flow control window for peer and send
      WINDOW_UPDATE frame with new fcw value
* new ':limits' constant MAX_FCW_SIZE to detect overflow of fcw counter
* fixed MAX_PAYLOAD_SIZE constant
* Stream changes:
    + stream_error() - send RST_STREAM to peer
    + stream_fcw_send/stream_fcw_recv - update fcw counters
    + stream_fcw_update() - increase fcw for peer and send WINDOW_UPDATE frame
      with new fcw value
    + stream_blocked_data() - save blocked data and issue BLOCKED frames
    + stream_send_blocked() - send blocked frames for stream
Update Server/Client for new send_headers/send_data/stream_error methods
update module status
update Changes
Checking in changes prior to tagging of version 0.05.

Changelog diff is:

diff --git a/Changes b/Changes
index 3863135..46bc4e1 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,8 @@ Revision history for Perl extension Protocol-HTTP2

 {{$NEXT}}

+0.05 2014-05-11T11:19:57Z
+
     - implemented flow control
     - implemented WINDOW_UPDATE encoder/decoder
     - fixed MAX_PAYLOAD_SIZE constant