Performance improvements by package updates / replacement

[fungilation]

• node-lodash (deprecation warnings in npm) replaced with latest lodash
• replaced sentence-tokenizer with sbd … about 50% faster performance, and better tokenizing! (don't consider stopwords like Mr. as end of sentences)
• sentences_dict cached and passed to getSentencesRanks from public exports (.summarize, .getSortedSentences), to avoid reprocessing same content between calls
• code styling based on JavaScript Standard Style
• mocha, should updated
• passing mocha tests: babel added for es6 imports, 3rd mocha test failed on undeclared var sorted_sentences... eliminated
• also added yarn.lock, .babelrc

[jbrooksuk]

Can you also update the .travis.yml file so we can see tests pass, please? :)

[fungilation]

Had to do more than just updating .travis.yml. All tests now passing.

A sidenote while I looked at optimizing performance for node-summary. I haven't dug much into the actual algorithm in summary.js, but note that I'm still having to resort to limiting summarization to first 70000 characters per article that I'm summarizing in my react native app. So as to limit processing time to roughly 5s per such 70000 chars text, as tested on a iPhone 6s.

Pointers to further optimization in the processing itself would be appreciated. Short of rewriting it in Swift/Java for mobile app use in my case...

[jbrooksuk]

Thanks for this!