parsing args issue if value starts with dash(-) character

[kodekracker]

Steps to reproduce

Save this snippet as example.js

var argv = require('yargs-parser')(process.argv.slice(2))
console.log(argv)

If we run the file by passing these arguments, then we are getting expected result of both arguments i.e foo as 33 and bar as hello

$ node example.js --foo=33 --bar "hello"
{ _: [], foo: 33, bar: 'hello' }

But, if we pass bar argument value whose starting character is -, then output changes a lot, and it's also not a expected one

$ node example.js --foo=33 --bar "-hello"
{ _: [],
  foo: 33,
  bar: true,
  h: true,
  e: true,
  l: [ true, true ],
  o: true }

Here, foo argument has correct value but bar argument value is now boolean.

Expected output in both instructions

{ _: [], foo: 33, bar: 'hello' }

[bcoe]

closing in favor of #145, please feel free to join the conversation there.