Reorganize codebase

[mcmire]

In attempting to detail the architecture of this codebase, I realized that it would be easier if the parts of SuperDiff that implemented differs, inspection tree builders, operation tree builders, operation tree flatteners, and operation trees for Ruby objects were split off into their own directory. To that end, alongside RSpec, ActiveRecord, and ActiveSupport, there is now a "Basic" feature module. In addition, to make the file structure a little flatter, I've also renamed InspectionTreeBuilders in various feature modules up one level (so, ObjectInspection::InspectionTreeBuilders is now simply InspectionTreeBuilders).

Following this change, SuperDiff can now be divided into 4 layers (here I'm putting CSI in brackets because it's not a public module):

          ----------------- [SuperDiff::CSI]
        /                     /     |
       /           SuperDiff::Core ----------------------
      |              /    |     \   |                    \
      |       /^^^^^^     |  SuperDiff::Basic             \
      |      /            |   /     |     \                \
      |     | /^^^^^^^^^^^|^^^^     |      ^^^^^^^^^^^^^\   \
SuperDiff::RSpec         SuperDiff::ActiveRecord     SuperDiff::ActiveSupport

Here is a full list of renames:

• The following constants that were previously available under SuperDiff are now located under SuperDiff::Core:
  • ColorizedDocumentExtensions
  • Configuration
  • GemVersion
  • Helpers
  • ImplementationChecks
  • Line
  • RecursionGuard
  • TieredLines
  • TieredLinesElider
  • TieredLinesFormatter
• Everything under SuperDiff::Differs is now under SuperDiff::Basic::Differs
• All error classes under SuperDiff::Errors have been moved out and are now directly under SuperDiff::Core
• SuperDiff::ObjectInspection::InspectionTree is now SuperDiff::Core::InspectionTree
• Everything under SuperDiff::ObjectInspection::InspectionTreeBuilders is now under SuperDiff::Core::InspectionTreeBuilders
• Everything under SuperDiff::ObjectInspection::Nodes is now under SuperDiff::Core::InspectionTreeNodes
• Everything under SuperDiff::OperationTreeBuilders is now under SuperDiff::Basic::OperationTreeBuilders
• Everything under SuperDiff::OperationTreeFlatteners is now under SuperDiff::Basic::OperationTreeFlatteners
• Everything under SuperDiff::OperationTrees is now under SuperDiff::Basic::OperationTrees
• Everything under SuperDiff::Operations has been moved out and is now directly under SuperDiff::Core
• Everything under SuperDiff::ActiveRecord::ObjectInspection::InspectionTreeBuilders is now under SuperDiff::ActiveRecord::InspectionTreeBuilders
• Everything under SuperDiff::ActiveSupport::ObjectInspection::InspectionTreeBuilders is now under SuperDiff::ActiveSupport::InspectionTreeBuilders
• Everything under SuperDiff::RSpec::ObjectInspection::InspectionTreeBuilders is now under SuperDiff::RSpec::InspectionTreeBuilders

To maintain backward compatibility, I've left all of the original constants in place, but they will now print deprecation warnings when used. I will remove them in 1.0.0.