Fix HttpProxySocket early data return value

Disable logging in example caddy.json

Add PGO build for Win and Mac

Add arm_cortex-a9 build

Update README.md

h2: Pad RST_STREAM frames

Clients sending too many RST_STREAM is an irregular behavior.

Hack in a preceding END_STREAM DATA frame padded towards [48, 72]
before RST_STREAM so that the TLS record looks like a HEADERS frame.

The server often replies to this with a WINDOW_UPDATE because padding
is accounted in flow control. Whether this constitudes a new irregular
behavior is still unclear.

Add option for concurrent transport

Useful only for high-end situations where a single connection
is throttled at 10MB/s somehow.

Makes traffic obfuscation less secure.

Add --extra-headers option

Add continuous integration and tests

Handle payload data immediately after HTTP headers

In HttpProxySocket there can be data immediately after HTTP headers,
as in the case of fast HTTP CONNECT.

Instead of reporting an error, handle this case by returning
the data after HTTP headers in the next Read() call.