docs(CHANGELOG): update for v0.4.0

CHANGELOG.md

 # go-graphsync changelog
 
+# go-graphsync 0.4.0
+
+Feature release - add memory backpressure to responses to minimize extra memory usage
+
+### Changelog
+
+- github.com/ipfs/go-graphsync:
+  - docs(CHANGELOG): update for 0.3.1 ([ipfs/go-graphsync#112](https://github.com/ipfs/go-graphsync/pull/112))
+  - Update ipld-prime (#111) ([ipfs/go-graphsync#111](https://github.com/ipfs/go-graphsync/pull/111))
+  - Add allocator for memory backpressure (#108) ([ipfs/go-graphsync#108](https://github.com/ipfs/go-graphsync/pull/108))
+  - Shutdown notifications go routines (#109) ([ipfs/go-graphsync#109](https://github.com/ipfs/go-graphsync/pull/109))
+
+### Contributors
+
+| Contributor | Commits | Lines ± | Files Changed |
+|-------------|---------|---------|---------------|
+| Hannah Howard | 3 | +724/-83 | 18 |
+
+
 # go-graphsync 0.3.1
 
 Security fix -- switch to google protobufs

responsemanager/allocator/allocator_test.go

@@ -3,11 +3,12 @@ package allocator_test
 import (
 	"testing"
 
-	"github.com/ipfs/go-graphsync/responsemanager/allocator"
-	"github.com/ipfs/go-graphsync/testutil"
 	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/ipfs/go-graphsync/responsemanager/allocator"
+	"github.com/ipfs/go-graphsync/testutil"
 )
 
 func TestAllocator(t *testing.T) {