LDA: Latent Dirichlet Allocation

Version 0.1.0 of this library is in development.

Proposed API.

```rust use lda::{Library, StopWords, Lda, LdaArgs, LdaAlgorithm};

let library = Library::frompath("my-docs.txt") .stopwords(StopWords::English) .minwordoccurance(10) .build();

let ldaargs = LdaArgs { alpha: 0.5, beta: 0.5, ntopics: 4 };

let mut lda = Lda::new(&library, lda_args);

let mut rng = rand::thread_rng();

lda.fit(1_000, LdaAlgorithm::Gibbs, &mut rng); ```