add UseTransformer
minor #915 add UseTransformer (keradus)

This PR was squashed before being merged into the 2.0-dev branch (closes #915).

Discussion
----------

add UseTransformer

add UseTransformer

Resolve #896

- [X] tests
- [X] skeleton
- [x] implementation
- [x] update Tokenizer
- [x] update Fixers
- [x] rebase after merge of #917

Commits
-------

febadf5 add UseTransformer
add ArraySquareBraceTransformer
minor #916 add ArraySquareBraceTransformer (keradus)

This PR was squashed before being merged into the 2.0-dev branch (closes #916).

Discussion
----------

add ArraySquareBraceTransformer

add ArraySquareBraceTransformer

Resolve #913

- [X] tests
- [X] skeleton
- [x] implementation
- [x] update Tokenizer
- [X] update Fixers
- [x] rebase after merge of #917

Commits
-------

53a6ee1 add ArraySquareBraceTransformer