Added ability to use library in webbrowser with requiring stopwords files

[ageitgey]

This is a PR of a commit from @cjanietz

@cjanietz are you ok with me pulling this in?

[cjanietz]

Go ahead, fine for me

[mazmazz]

I suggest this line should be hasFs = fs and fs.existsSync.

The current line fails because the compiled JavaScript line treats fs as an array with length, and fs.length does not exist:

function in$(member, list) {
  for (var i = 0, length = list.length; i < length; ++i) // <-- failure at list.length
    if (i in list && list[i] === member)
      return true;
  return false;
}
hasFs = in$('existsSync', fs);

The proposed change succeeds in JavaScript as hasFs = fs && fs.existsSync. This should fix the buildbots.

I would PR to the branch myself, but I'm unfamiliar with CoffeeScript and can't build.

[justinmchase]

Maybe drop fs entirely and convert the stop word files to code:

# en.coffee
module.exports = [
  "a's",
  "able",
  # ... etc.
]

stopwords = require(language)