Pybryt

* Added tracking and warnings for errors in student notebook execution
* Added the `matrix_transpose` and `list_permutation` invariants
* Fixed code tracing at top level in the `check` context manager
* Added `pybryt.ReferenceImplementation.get` for looking up annotations by name

* Fixed bug in `Value` annotations regarding NaN values

* Added the `Collection` annotation

* Added the `ForbidType` annotation

* Added the context manager `pybryt.no_tracing`
* Added caching to `pybryt.check`
* Added scaffold for custom complexity classes

* Added time complexity annotations and checking
* Changed tracing function to only increment step counter when tracing student code
* Added relative tolerance to value annotations
* Fixed bug in intermediate variable preprocessor for newer versions of Python
* Added a context manager for checking code against a reference implementation from the same
notebook
* Added a CLI for interacting with PyBryt