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/urls.go b/openstack/blockstorage/v2/extensions/volumeactions/urls.go
index 4ddcca0..a61ee7d 100644
--- a/openstack/blockstorage/v2/extensions/volumeactions/urls.go
+++ b/openstack/blockstorage/v2/extensions/volumeactions/urls.go
@@ -25,3 +25,7 @@
 func teminateConnectionURL(c *gophercloud.ServiceClient, id string) string {
 	return attachURL(c, id)
 }
+
+func extendSizeURL(c *gophercloud.ServiceClient, id string) string {
+	return attachURL(c, id)
+}