rewrote import paths of go.net/context to use golang.org/x/context

- updated go-ctxgroup and goprocess
ctxgroup: AddChildGroup was changed to AddChild. Used in two files:
- p2p/net/mock/mock_net.go
- routing/dht/dht.go

- updated context from hg repo to git
prev. commit in hg was ad01a6fcc8a19d3a4478c836895ffe883bd2ceab. (context: make parentCancelCtx iterative)
represents commit 84f8955a887232b6308d79c68b8db44f64df455c in git repo

- updated context to master (b6fdb7d8a4ccefede406f8fe0f017fb58265054c)

Aaron Jacobs (2):
net/context: Don't accept a context in the DoSomethingSlow example.
context: Be clear that users must cancel the result of WithCancel.

Andrew Gerrand (1):
go.net: use golang.org/x/... import paths

Bryan C. Mills (1):
net/context: Don't leak goroutines in Done example.

Damien Neil (1):
context: fix removal of cancelled timer contexts from parent

David Symonds (2):
context: Fix WithValue example code.
net: add import comments.

Sameer Ajmani (1):
context: fix TestAllocs to account for ints in interfaces

merkledag.go

@@ -6,8 +6,7 @@ import (
 	"sync"
 	"time"
 
-	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
-
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
 	blocks "github.com/jbenet/go-ipfs/blocks"
 	bserv "github.com/jbenet/go-ipfs/blockservice"
 	u "github.com/jbenet/go-ipfs/util"

merkledag_test.go

@@ -8,9 +8,9 @@ import (
 	"sync"
 	"testing"
 
-	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
 	dssync "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/sync"
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
 	bstore "github.com/jbenet/go-ipfs/blocks/blockstore"
 	blockservice "github.com/jbenet/go-ipfs/blockservice"
 	bserv "github.com/jbenet/go-ipfs/blockservice"