Former kgram_freqs class is now called sbo_kgram_freqs. The constructor kgram_freqs() is still available as an alias to sbo_kgram_freqs().

Former sbo_preds class is now substituted by two classes:

  - `sbo_predictor`: for interactive use
  - `sbo_predtable`: for storing text predictors out of memory (e.g. 
  `save()` to file)

sbo_predictor and sbo_predtable objects are obtained by the homonym constructors, which are now S3 generics accepting character input, as well as sbo_kgram_freqs and sbo_predtable (for the sbo_predictor() constructor) class objects. In particular, these allow to directly train a text predictor without storing the intermediate sbo_dictionary, and kgram_freqs objects.

The behaviour of the dict argument in kgram_freqs() and kgram_freqs_fast() has changed, now accepting either a sbo_dictionary, a character or a formula (see also ‘New features’).

The sbo_predictor implementation dramatically improves the speed of predict() (by a factor of x10). A single call to predict() now allocates a few kBs of RAM (whereas it previously allocated few MBs, c.f. issue #10).

Metadata of sbo_kgram_freqs and sbo_pred* objects is now stored via attributes (#11).