undescore removes _

[maciejmyslinski]

Hey there!

I just found inflection.underscore('_') returns '' (an empty string).

I bet it's a bug since this method should add, not remove, underscores.

Once confirmed by the author, I'm happy to implement a fix.

[maciejmyslinski]

FYI here is a code for a test that found that bug:

const inflection = require('inflection');
const fc = require('fast-check');

describe('inflection', () => {
  it('underscores properly', () => {
    fc.assert(
      fc.property(fc.string(), text => {
        const underscored = inflection.underscore(text);
        expect(underscored.length).toBeGreaterThanOrEqual(text.length);
      }),
      { numRuns: 10000 }
    );
  });
});