Remove obsolete todo
Add examples for ISO8601::Duration
Expose Duration#pattern
Add Duration#atomize to wrap parsing logic for durations
Change instance variables to public methods when possible
Refactor Duration#to_seconds to be more expressive
Fix Duration#abs so it uses the right base
Refactor #+ and #-
Extract #compare_bases
Refactor #sign
Refactor Duration#atomize
Change Array#to_h to Hash[] to support 1.9.3 and 2.0
Add Duration#eql? to improve equality
Add test to ensure hash identity by value
Fix Duration#== test
Change rspec to expect()
Add explicit RSpec
Change Duration#== to use hash for equality
Change #== and #eql? so the later uses hash for identity
Change validate_base strategy