luz 0.2.0

New features

Allow users to provide the minimum and maximum number of epochs when calling fit.luz_module_generator(). Removed ctx$epochs from context object and replaced it with ctx$min_epochs and ctx$max_epochs (#53, @mattwarkentin).
Early stopping will now only occur if the minimum number of training epochs has been met (#53, @mattwarkentin).
Added cuda_index argument to accelerator to allow selecting an specific GPU when multiple are present (#58, @cmcmaster1).
Implemented lr_finder (#59, @cmcmaster1).
We now handle different kinds of data arguments passed to fit using the as_dataloader() method (#66).
valid_data can now be scalar value indicating the proportion of data that will be used for fitting. This only works if data is a torch dataset or a list. (#69)
You can now supply dataloader_options to fit to pass additional information to as_dataloader(). (#71)
Implemented the evaluate function allowing users to get metrics from a model in a new dataset. (#73)

Fixed bug in CSV logger callback that was saving the logs as a space delimited file (#52, @mattwarkentin).
Fixed bug in the length of the progress bar for the validation dataset (#52, @mattwarkentin).
Fixed bugs in early stopping callback related to them not working properly when patience = 1 and when they are specified before other logging callbacks. (#76)

ctx$data now refers to the current in use data instead of always refering to ctx$train_data. (#54)
Refactored the ctx object to make it safer and avoid returing it in the output. (#73)