README.md: Remove obsolete note on Transfer-Encoding: chunked
PubNub: Use (const char *) in many places instead of (char *)
PubNub::_request_bh(): Store chunked_str[] in PROGMEM
examples/PubNubJson: Mark some of the variables as static const
examples/PubNubJson: Tighten msgStr memory buffer
examples/PubNubJson: Describe more memory saving tips