Replaced instances of resize&memcpy with append, which gives a noticeable performance boost.
fr::Packet::operator<<(const char *str) no longer converts str into an std::string before adding it, removing an unneeded copy.
fr::Packet::clear no longer calls erase, should result in more of the internal buffer remaining allocated.
Framing for std::vector's has been changed from a uint64_t to a uint32_t (breaking change for packet framing!)
