fixing clusters API when using user-level API

When using the user-level API (filtered view), we need to return all the
cluster the user sees, rather than only clusters in the current DC.
This patch fixes that issue (returning the cluster in case it is either
a filtered view, or in the current DC).
Merge pull request #14 from oourfali/cluster_api

fixing clusters API when using user-level API
Release 0.0.17
Added status attribute to Network
Merge pull request #15 from jprovaznik/status_attr

Added status attribute to Network
ignore missing vm link in volumes.
Regenerate gemspec for version 0.0.17
Version bump to 0.0.18
Regenerate gemspec for version 0.0.18