Only call process.nextTick if it's defined

[jvanalst]

Adding this check allows the library to be used outside of node.js.

This is very useful for me, because I'd like to try and use step.js on a front end application to help keep my code as clean as possible.

[trungpham]

it would be cool if we can use step in the browser instead of async, which is a bit bloated for what it is trying to do.

[aeosynth]

setTimeout works in node; you can be really lazy by skipping the check and just replacing process.nextTick.

[bminer]

@aeosynth - Agreed. Just replace process.nextTick with setTimeout(..., 0) altogether. Optionally, add a comment to the code for clarity.

[boomla]

process.nextTick once gave me an over 10x speed increase. I would never ever even consider using setTimeout again - except in the browser of course.