Include sphinx_rtd_theme to distribution

Patch from Dave Beckett
Remove sphinx_rtd_theme/static/font

Which was moved to spinx_rtd_theme/static/fonts
Add missing nghttp2.h.rst and nghttp2ver.h.rst to EXTRA_DIST
Merge branch 'master' into draft-10
Run test after doc so that we can see test result in terminal
Add nghttp2_frame_add_pad to deal with adding pads
Handle incoming PAD_HIGH and PAD_LOW in inbound_frame_handle_padding
Update flags
Fix bufoff_ptr if no padding is made
Implement padding for HEADERS and CONTINUATION
Add test for nghttp2_frame_pack_headers with padding
Update doc
Fix on_frame_recv_callback called multiple times if CONTINUATION is involved
Merge branch 'master' into draft-10