[parser] Allow newlines as separators in blah[...]
[np] fix hash_arg sexp generation
[np] Fix method chain sexp generation

inserted last call in wrong place because
node name is no longer a node element
[np] Add sexp.==
[np] Return self for sexp.<< and sexp.concat
[np] program ast doesn't need :body
[test] Switch to sexps for AST tests