Updated Post Sockets draft submitted to IETF

We've submitted an updated draft describing Post Sockets (draft-trammell-taps-post-sockets-00) to the IETF. The changes in this version reflect the outcome of the meeting held at ETH Z├╝rich in February.

Compared to the previous version, the draft has been almost completely rewritten. The core concepts remain, but there are numerous clarifications and improvements to the design. The draft filename has been changed to include -taps- to reflect the interest of the TAPS working group in following this work.