Adds block storage extend's action support (#67)

* created Godeps dependency tree

* added vendor folder to gitignore

* added support for extend size action to volumes's client

* Revert "created Godeps dependency tree"

This reverts commit b9366e292c2e99e262240b98151c98f49c69df32.

* Revert "added vendor folder to gitignore"

This reverts commit 34403f85dad4f0514d7e0d8ce882b1712b82cd87.

* set volumeactions.ExtendSizeOpts.NewSize as required
diff --git a/openstack/blockstorage/v2/extensions/volumeactions/results.go b/openstack/blockstorage/v2/extensions/volumeactions/results.go
index 9bf6a7b..f9e8120 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/results.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/results.go
@@ -44,3 +44,8 @@
 type InitializeConnectionResult struct {
 	commonResult
 }
+
+// ExtendSizeResult contains the response body and error from an ExtendSize request.
+type ExtendSizeResult struct {
+	gophercloud.ErrResult
+}