Modularize NullColorizer

Other colorizers s.t. ConsoleCodes are module with module_functions.
NullColorizer was a class and the class does not respond to `wrap()`.
This patch fixes the mismatch.
Fix hash notation for Ruby 1.8
Clarify changelog entry.

[ci skip]
Merge pull request #1689 from tomykaira/modularize_NullColorizer

Modularize NullColorizer
cleanup and changelog for 1689
Fix typo in ExampleGroup comment
Merge pull request #1690 from zhangsu/patch-1

Fix typo in ExampleGroup comment
Fix regression in rake task pattern option.

Fixes #1691.
Shellescape rake task patterns.
Handle `pattern = ./path/to/spec.rb` as well.

For #1691.
Merge pull request #1692 from rspec/fix-rake-task-pattern-regression

Fix rake task pattern regression
3.1.0 release.
Bump version to 3.2.0.pre.
Fix another regression in rake task pattern handling.

This was reported by @aprescott: https://github.com/rspec/rspec-core/pull/1671#issuecomment-54623310.

The regression was originally introduced in #1653.
See also #1691 and #1692.
3.1.1 has been released.
Single glob patterns that start with ./ don't match any files.
Tweak for consistent whitespace.
Tweak for consistent handling of multi-element array formatting.
Forward port 3.1.2 release notes.

[ci skip]
Add better `inspect` output for ExampleGroup

Changing from defining a singleton method to storing the inspect output on the ExampleGroup

Add documentation for instance_variables and inspect

Handling string element in instance_variables for ruby 1.8

Removing un-needed expct calls in spec

Handling ExampleGroup without inspect output, handling ExampleGroup without a description, refactoring logic to ignore `@__inspect_output` when determining before context ivars

Improve readability of no inspect output spec and does not copy inspect output from before context to examples spec