Ability to escape equal signs in parameter value

Is there a reason you split on equal signs?

https://github.com/sgmonda/stdio/blob/master/main.js#L18

I am using this on a recent project and needed to be able to pass a url as an option (with get parameters) and this threw me for a loop.

I change that check to this:

https://github.com/truckingsim/stdio/blob/master/main.js#L18-L25

Which lets me escape equal signs if I prepend a `\` in front of the equal sign.  Let me know if you see anything wrong with this.