net/p2p + secio: parallelize crypto handshake

Add option to allow unrestricted API access

We had a very nasty problem: handshakes were serial so incoming
dials would wait for each other to finish handshaking. this was
particularly problematic when handshakes hung-- nodes would not
recover quickly. This led to gateways not bootstrapping peers
fast enough.

The approach taken here is to do what crypto/tls does:
defer the handshake until Read/Write[1]. There are a number of
reasons why this is _the right thing to do_:
- it delays handshaking until it is known to be necessary (doing io)
- it "accepts" before the handshake, getting the handshake out of the
  critical path entirely.
- it defers to the user's parallelization of conn handling. users
  must implement this in some way already so use that, instead of
  picking constants surely to be wrong (how many handshakes to run
  in parallel?)

[0] http://golang.org/src/crypto/tls/conn.go#L886

Refactor/http gateway

(I'll add the changelog later today)

Refactor/http gateway quickfix (1191)

some golinting along the way

- NewDagReader() used the wrong context
- Ip?sPathPrefix isn't used anywhere
- a little bit of error handling cleanup

path/resolver: Fix recursive path resolution

Setup a three-level graph:

  a -(child)-> b -(grandchild)-> c

and then try and resolve:

  /ipfs/<hash-of-a>/child/grandchild

Before 10669e8b (path/resolver: Fix recursive path resolution,
2015-05-08) this failed with:

  resolver_test.go:71: no link named "grandchild" under QmSomeRandomHash

The boilerplate for this test is from pin/pin_test.go, and I make no
claims that it's the best way to setup the test graph ;).

I'm not entirely clear on Go's scoping (there's some text I can't
quite parse here [1]), but it seems like the := version (because this
is the first time we use 'err') was masking the function-level 'nd'
just for this if block.  That means that after we get out of the if
block and return to the start of the for-loop for the next pass,
nd.Links would still be pointing at the original object's links.

This commit drops the :=, which fixes the earlier:

  $ ipfs ls QmXX7YRpU7nNBKfw75VG7Y1c3GwpSAGHRev67XVPgZFv9R/static/css
  Error: no link named "css" under QmXX7YRpU7nNBKfw75VG7Y1c3GwpSAGHRev67XVPgZFv9R

so we get the intended:

  $ ipfs ls QmXX7YRpU7nNBKfw75VG7Y1c3GwpSAGHRev67XVPgZFv9R/static/css
  Qme4r3eA4h1revFBgCEv1HF1U7sLL4vvAyzRLWJhCFhwg2 7051 style.css

It also means we're probably missing (or are unreliably using) a
multi-level-path-resolving test.

[1]: https://golang.org/ref/spec#Declarations_and_scope

core: add context.Context param to core.Resolve()

godeps: update metrics (freebsd build fix)

add link to community contributing #1088

godeps: rewrite import path

commands/object: remove objectData() and objectLinks() helpers
resolver: added context parameters
sharness: $HASH carried the \r from the http protocol with
sharness: write curl output to individual files
http gw: break PUT handler until PR#1191

ipnsfs/system: Fix 'retreive' -> 'retrieve' typo

From 93b06f34 (Add timeout to ipns resolution at startup, 2015-04-24,
#1133).

mild refactor of bitswap

correct the blocksize calculation for link blocks

update hash for bigfile

make comments match the code in secure channel implementation

quick fix for OOM panic that has been plaguing us

try harder to not send duplicate blocks

increase iptb test stability

fix append bug and overwrite/truncate bug

update iptb dependency again, and pick different ports for each iptb cluster

try and fix godeps crap

Improve parse_test.go