[Fix #943] Fix auto-correct interference with SpaceAfterComma

The SpaceAfterComma (and possibly other cops that include
SpaceAfterPunctuation) can destroy code if other cops are auto-
correcting in the same area. The solution is to make a bigger
substitution, so conflict resolution logic kicks in.
Merge pull request #951 from jonas054/fix_943_autocorrect

[Fix #943] Fix auto-correct interference with SpaceAfterComma
failing test case for NilComparison autocorrect
[Fix #954] Auto-correct `x === nil` in NilComparison
failing test case for NonNilCheck
[Fix #953] Auto-correct properly code like `!nil?` in NonNilCheck
Add failing test case for StringConversionInInterpolation
[Fix #952] Handle implicit receiver in StringConversionInInterpolation
proper failing test case for ClassMethods
[Fix #956] Apply ClassMethods check only on class/module bodies