Add support for tags parameter to cloudformation module

Expose boto.cloudformation.create_stack() tags parameter. Supplied tags
will be applied to stack and all it's resources on stack creation.
Cannot be updated later (not supported by UpdateStack CloudFormation
API).
Add Boto version check for tags parameter of cloudformation module

Tags parameter requires at least version 2.6.0 of Boto module. When tags
parameter is used with older version, error is raised. When tags
parameter is unused, module works as before.
Add version_added to cloudformation tags parameter
Merge pull request #4272 from psvo/tags_parameter_for_cloudformation

Add support for tags parameter to cloudformation module