Stop scrolling when top or bottom is reached

[lucasicf]

Fixes #5.

[Schabernack]

any intention of merging these changes in? this issue is particularly annoying and reason alone to abandon an otherwise very helpful plugin.

[ryanoasis]

:+1:

[danijar]

+1

[lucasicf]

+1. Any updates here?

[Wsine]

+1, please merge, it's good

[lucasicf]

Hi. Any updates?

In the meanwhile I've got https://github.com/lucasicf/vim-smooth-scroll with this commit. I'd like this merged here though.

[KeshiSmith]

I fixed #5 in another way. Using original scrolling of vim instead of simulation. Branch: KeshiSmith/vim-smooth-scroll