starting to add sexp encoder
add hygiene support fns, move them around.
tmp -- but compiles!
tmp
tmp
tmp
expansion now covers macros, test cases for renaming
removed unneccessary SyntaxExpander structs
separate ItemDecorator from ItemDecorator
refactor so tt_fold only requires an ident->ident fn
adding test case to check marking/unmarking
comment
comment
comment
one-line comment
added parse_token_trees.rs