Update jquery.scrollUp.js

[kouratoras]

Option to add a custom class to element

[markgoodyear]

Thanks for the PR @kouratoras. Just out of curiosity, what is the reason for needing a class?

[kouratoras]

I am building a WordPress plugin based on ScrollUp jQuery Plugin and i want to assign a class in the scroll up element, depending on the user's settings. So, just an ID is not enough for me, as i want to apply different styles. I think that class addition would be useful for situations like mine.

[markgoodyear]

Makes sense :) Would you be able to compile the distribution files? Check out the CONTRIBUTE.md file. If you can't compile, I'll merge it in over the weekend.

[kouratoras]

It's the first time i use gulp. I just change the src/jquery.scrollUp.js file and run gulp to complile? I does not change dist files..

[markgoodyear]

Are there any errors? I'll close this PR and add it in. Will create some better contribution docs too :)

[kouratoras]

No error, just no modified output files.

[kouratoras]

Hi! Did you close the PR?

[markgoodyear]

I've not merged it in as I've not had chance to check everything out and build out the files yet. I'll look into this hopefully tonight :)