images service v2 port from rackpsace/gophercloud (#171)

* CheckByteArrayEquals funcs

* direct port from rackspace/gophercloud with minor additions to get unit tests passing

* new package for uploading and downloading image data

* updates to make imageservice v2 consistent with the rest of gophercloud/gophercloud

* add image service v2 client
diff --git a/openstack/imageservice/v2/imagedata/testing/requests_test.go b/openstack/imageservice/v2/imagedata/testing/requests_test.go
new file mode 100644
index 0000000..4ac42d0
--- /dev/null
+++ b/openstack/imageservice/v2/imagedata/testing/requests_test.go
@@ -0,0 +1,87 @@
+package testing
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"testing"
+
+	"github.com/gophercloud/gophercloud/openstack/imageservice/v2/imagedata"
+	th "github.com/gophercloud/gophercloud/testhelper"
+	fakeclient "github.com/gophercloud/gophercloud/testhelper/client"
+)
+
+func TestUpload(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+
+	HandlePutImageDataSuccessfully(t)
+
+	err := imagedata.Upload(
+		fakeclient.ServiceClient(),
+		"da3b75d9-3f4a-40e7-8a2c-bfab23927dea",
+		readSeekerOfBytes([]byte{5, 3, 7, 24})).ExtractErr()
+
+	th.AssertNoErr(t, err)
+}
+
+func readSeekerOfBytes(bs []byte) io.ReadSeeker {
+	return &RS{bs: bs}
+}
+
+// implements io.ReadSeeker
+type RS struct {
+	bs     []byte
+	offset int
+}
+
+func (rs *RS) Read(p []byte) (int, error) {
+	leftToRead := len(rs.bs) - rs.offset
+
+	if 0 < leftToRead {
+		bytesToWrite := min(leftToRead, len(p))
+		for i := 0; i < bytesToWrite; i++ {
+			p[i] = rs.bs[rs.offset]
+			rs.offset++
+		}
+		return bytesToWrite, nil
+	}
+	return 0, io.EOF
+}
+
+func min(a int, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func (rs *RS) Seek(offset int64, whence int) (int64, error) {
+	var offsetInt = int(offset)
+	if whence == 0 {
+		rs.offset = offsetInt
+	} else if whence == 1 {
+		rs.offset = rs.offset + offsetInt
+	} else if whence == 2 {
+		rs.offset = len(rs.bs) - offsetInt
+	} else {
+		return 0, fmt.Errorf("For parameter `whence`, expected value in {0,1,2} but got: %#v", whence)
+	}
+
+	return int64(rs.offset), nil
+}
+
+func TestDownload(t *testing.T) {
+	th.SetupHTTP()
+	defer th.TeardownHTTP()
+
+	HandleGetImageDataSuccessfully(t)
+
+	rdr, err := imagedata.Download(fakeclient.ServiceClient(), "da3b75d9-3f4a-40e7-8a2c-bfab23927dea").Extract()
+	th.AssertNoErr(t, err)
+
+	bs, err := ioutil.ReadAll(rdr)
+	th.AssertNoErr(t, err)
+
+	th.AssertByteArrayEquals(t, []byte{34, 87, 0, 23, 23, 23, 56, 255, 254, 0}, bs)
+}