[xenserver|compute] added destroy_network request
[xenserver|compute] added destroy_network request tests
fix syntax, ruby 1.8.7
[xenserver|compute] added VLAN model and tests
[xenserver|compute] Added Vlans collection and tests
[xenserver|compute] added save and destroy operations to Network

- Added also required tests
[xenserver|compute] updated compute service to add new model, requests

- added VLAN model
- added Vlans collection
- added create_network request
- added create_vlan req.
- added destroy_network req.
- added destroy_vlan req.
[xenserver|compute] Added Network/VLANs creation example
[openstack|network] mock fixes in some OpenStack Network requests

Updated mocks in some network request fixing some issues and keeping
the mocking style used in other requests.
Merge pull request #1700 from bvox/xenserver-network-additions

Xenserver network additions
Merge pull request #1698 from dm1try/master

[cloudstack] add snapshot model
fix internet archive use of headers, remove acls
Merge pull request #1634 from PRX/internet_archive

[Internet Archive] handle IA specific headers
put extra keys in fog credential error.
Merge pull request #1701 from rubiojr/openstack-network-mock-fixes

[openstack|network] mock fixes in some OpenStack Network requests
Merge pull request #1632 from rubiojr/multiple-accounts-support

[openstack|storage] Added support to impersonate other accounts
[openstack|compute] Add volume attachment methods
[rackspace] added exception info to rackspace api documentation
Merge branch 'master' of github.com:fog/fog into ready_exception
Merge branch 'master' of github.com:fog/fog into exception_doc