* Reduce implementation
* Fix assumption node specific classes under AST::Meta all have
#assignable? method. They are intentionalyl not LSP compatible and do
NOT share the class hierarchy for that reason.
* Inline APIs with one call side
* Add Mutant::AST namespace to hold all AST related data / helpers.
* Mutant::AST will be externalized into an ast-meta gem that can be
shared with unparser for deduplication.
* Over the time the mutators itself will not need to deal with semantic
analysis of the AST anymore by themselves.
* Move AST analysis for send nodes to AST::Meta
* Fix#209
* I do not use 1.9.3
* Also keeping them in each file increases mental overhead (true it *can* be autoamted)
* None of the files encodes NON ASCII chars.
* I do not expect it makes any difference, since nobody programmatically
will consume strings generated by mutant under the assumption they are UTF-8 encoded.
* 1.9.3 Users have to deal with the encoding fuckup under ruby anyways.
