Added slide padding option, and fixed transition bug

Wanted slides to have padding, but keep with the code that updates width
for responsive. Added in a settings section to allow that, and modified
the returned width for getSlideWidth() appropriately.

Using basic slideshow, using previous button from start slide to last,
the transition didn't end smoothly. Instead it went too far, then
snapped to the right spot after updating. Found that code block at line
1126 corrected this issue, though I was not in carousel mode. As such,
proposing to take out that carousel check entirely. ** I'm not sure how
this will affect other things? It fixes a very basic issue for me that I
don't know how this slider would function otherwise. **