Feat
- **functions.py**: added `gelu` function
Fix
- **basic.py**: fix bug in `null_log_likelihood_fn` for givens
- **dataset.py**: fixed slice call when no `batch_size` argument is used
- **dataset.py**: fixed the `split` method to accept `None` as argument
Refactor
- **functions.py**: refactored method to covert list of utilities to tensor variables
- **dataset.py**: accept mixed `str` and `TensorVariable` types in `_make_tensor`
- **basic.py**: moved `build_gh_fn()` to `BaseModel`