Remove environment warning

Hi, first of all - great plugin!

I've set it up and everything works great, but when I run gulp I get the warning "basicScroll is not executing because you are using it in an environment without a `window` object".

I'm a bit of a rookie so this could be something I have done. I've searched the error and similar errors on Google but couldn't find a fix. Any ideas?

Start by reproducing the warning when running gulp, then locate where basicScroll checks for a window object. Determine whether the warning is expected for the reported environment and what behavior should change; done means the warning is removed or clearly handled without breaking browser use.

Written by the indexing model from the issue text.