Dropping cucumber features

* Mostly skeletons and dummies
* Not used and outdated
Dropping cucumber tasks from Rakefile
Moved devel deps to Gemfile
Dropping legacy AMQP support

* Not maintained
* No AMQP-capable server available
* Might return in the future as a separate gem
Updated rOCCI-core to 4.2.0
Clean-up in the gemspec file

* Removed old references to cucumber features
Updated Keystone authN plugin

* Minor refactoring and clean-up
* Added support for `snf-auth`
* Fixes #15
Merge pull request #16 from arax/new_core

Staging for 4.2.0.beta.1
Updated #describe

* Returning Occi::Core::Resources
* Updated specs
* Updated examples
Bumped version to 4.2.0.beta.2
Merge pull request #17 from arax/desc_fix

Updated #describe, using Occi::Core::Resources
Updated mixin methods

* Working directly with model.mixins
* Using Occi::Core::* classes for mixins
* Added a few helper methods
* Updated specs
* Changed #find_mixin to #get_mixin
Updated examples
Merge pull request #19 from arax/mixin_fix

Updated mixin methods
Adding model to each new Resource instance
Merge pull request #20 from arax/model_res_fix

Adding model to each new Resource instance
Added custom errors and autoloading for errors
Added new error for stub methods from ClientBase
[WIP] Extensive changes in Client*, not yet ready
Updated @endpoint handling (URI -> String)