The function contains/include will cause the _.omit function deal with an array object incorrect

The "contains/include" function in original underscore could deal with array correct, such as `["apple","banana","orange"]`.
When search a key named "a", the original contains would return `-1`.
But the underscore.string recover the contains, and make the value of return is `0`, since it only use the follow function to make it to string simply.
`return '' + object;` in `module.exports`