Multiaddr interface feels weird to work with

[keks]

On IRC I mentioned that I would expect Push() and Pop() methods, and the idea came up to improve the general UX of the library.

22:34 < keks> is there a reason multiaddr doesn't have push() and pop()? push kind of is 
              Encapsulate, but decapsulate seems to be pop() except that it does the 
              opposite
22:34 < keks> you have to specify the ending and it gives you the beginning. aren't you 
              usually interested in the top of the protocol stack?
22:36 <@jbenet> keks: yeah, the multiaddr util funcs could be expanded.
22:52 <@whyrusleeping> keks: yeah... the multiaddr interface does feel a bit weird
22:53 <@whyrusleeping> should probably open an issue about improving the UX on that