[Review] Request from '' @ 'xystushi/git-review/use_hashie_instead_of_classes'

Please review the following changes:
  * 2532e47 Make sure it also works in subdirectories.
  * e1362ed Refactor EVERYTHING, and prepare for tests.
  * cac0051 Modify some class attributes
  * 0746fdf Add repositories and discussion method
  * 99d9f4b Some clean-ups
  * ea36798 Refactor prepare and create commands.
  * 8c348cd Refactor checkout, approve, merge, and close commands.
  * 6194ef9 Remove attr_accessors in Settings so that getters work properly
  * bef98d6 Refactor list, show, and browse command.
  * ccdec63 Check if the object is actually deserializable.
  * 89dd666 Remove initialize method and delegate it to Nestable
  * 08773e3 Fix typo
  * 1de4d17 Tests for clean_all and clean_single.
  * 5d4d831 Refactor "Clean" command.
  * 71a767d Move some git operations from Internals to Local class.
  * 280ed74 Refactor git-review and DRY up the spec
  * f224a66 Refactor git-review_spec into contexts.
  * 8dab119 User GirReview namespace.
  * eee0ead New git-review.
  * e46e347 Update README.md
  * 9f2596c Update README.md
  * 9d5ef32 Restructure files into GitReview module for cleaner namespacing.
  * b6dd62c Use grit to manage local repo
  * 61e328b Implement tests for github authentication.
  * ec35103 Implement github methods currently used in Internals.
  * caf70d6 Combine FatalError with UnprocessableState
  * cfbd5b3 Add to_s method to all models.
  * 0c84369 Use require_relative for local modules.
  * 66c3eca Move UnprocessableState into Errors module.
  * 1881833 Rename duplicate class names in tests to avoid conflict.
  * 014b5b1 Make sure models all have correct mixins and attributes.
  * 89d84f2 Inherit attributes list from superclass.
  * 79e50ad Implement login and pull_requests features of Github singleton.
  * f67dc90 Fix a serious bug in Deserializable.
  * 0dc6f4a Implement Deserializable mixin to conveniently update attributes from Mash returend by Octokit.
  * 47f7677 Create github singleton class.
  * e704f4d Update README.md
  * 72d4e88 Update README.md
  * e1b6731 Implement tests for github authentication.
  * 6703385 Implement github methods currently used in Internals.
  * 59fe6db Combine FatalError with UnprocessableState
  * afe0f12 Add to_s method to all models.
  * 8cbc620 Use require_relative for local modules.
  * 7b16e08 Move UnprocessableState into Errors module.
  * f458794 Rename duplicate class names in tests to avoid conflict.
  * 2324ed0 Make sure models all have correct mixins and attributes.
  * a4f0b27 Inherit attributes list from superclass.
  * 80362de Implement login and pull_requests features of Github singleton.
  * a2be5da Fix a serious bug in Deserializable.
  * e31250b Implement Deserializable mixin to conveniently update attributes from Mash returend by Octokit.
  * 6c1ee21 Create github singleton class.