Initial support for API versioning.

Resource version can be specified in resource controller or in one of parents controllers.
Parallel existence of one resource in more versions is supported - they have to be in separated
modules (see example in spec/dummy application).
Merge branch 'master' into api_versioning
Merge branch 'master' into api_versioning

Conflicts:
	lib/restapi/application.rb
Merge branch 'master' into api_versioning
Merge branch 'master' into api_versioning
Merge branch 'master' into api_versioning

Conflicts:
	lib/apipie/application.rb
	lib/apipie/resource_description.rb
	spec/controllers/users_controller_spec.rb
	spec/dummy/app/controllers/users_controller.rb
Restapi->Apipie
Support for API versioning #34

- option to specify default version
- list of versions on the homepage
- api_doc_url and app_info are version specific and can be filled
  in config file or in base controllers
- Apipie::Configuration separated to own file
- added config option debug
- methods are saved in its resource in hash
  no Apipie.method_descriptions anymore
- added 'version' argument to rake tasks, using default version if not specified
Small code readability improvements #34

+ it is now possible to turn of markup, we should use this when generating cli client.
Preserve methods order #34

Also there was quite a mess in symbol vs string use
Suggest: use symbols as hash keys
         use strings everywhere else
Updated rpm spec
Syntax highlighting for examples

No need to specify example format, prettify will guess.
closes #44
Disqus discussion support

if config.diqus_shortname is set, discussion is showed on every page
Merge pull request #54 from Pajk/disqus

Disqus discussion support
Render 404 error page when resource or method does not exist.
Merge pull request #58 from Pajk/handle_404

Render 404 error page when resource or method does not exist.
move template files to the same directory structure as it is generated
move generated abstract classes to apipie and require them from there
improve error structure by adding an ancestor

fix tests
fix OAuth signatures

parameters were not signed