Improve vcloud-curl usefulness

* Fix session handling
* Allow for more customisation of main query
* Remove '-k' curl opt. Not needed, insecure.
highlight that vcloud-curl is example code
First bash at vcloud-curl ruby script

* includes ability to get vcloud session token and api end_point from Fog
allow override of default curl opts (-s for now)
correct command name in usage
Merge pull request #52 from alphagov/vcloud-curl-tidy

vcloud-tool as ruby, shell version as 'example code'