Write new tutorials

[stephantul]

The API of wordkit has changed somewhat. Focus on the wordstore and the merging of corpora.

[stephantul]

Tutorials:

Corpora:

• [ ] Merge Subtlex with Lexicon projects
• [ ] Merge CELEX with other corpora
• [ ] Bilingual (cognates)

Featurization:

• [ ] Demonstrate easy featurization
• [ ] Show integration with sklearn pipelines

Sampler:

• [ ] Show sampling on basis of frequency