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Move deprecated into IceCube namespace

Closes #188
Mixin belongs in the inner Validation classes, not here
Use recent versions of RSpec for testing
Make RSpec 2.14 happy: stubs are doubles
Clean up metaprogramming for readability
Inline simple conditions
Standardize the exceptions that we raise
Put helpers in a module to clean up
Cleanup method order: initialize first
Cleanup method order: type after initialize
Cleanup method order: dst_adjust? before builders
Cleanup method order: validate before builders
Cleanup method order: build_s before other builders
Cleanup method order: build_hash, build_ical last
Clean up validate methods
Rename validation type for clarity
Documentation comments
Optimize for readability
All Rule types should take same arguments

For easier duck-typing. (More refactoring to come)