Fix modal to not shift/move the page upon closing

[EnoshAnwar]

When using the Modal component from pcln-modal on another application I noticed the page body shift to the left when closing the modal. This is something that can also be seen on priceline.com.

[oliviertassinari]

If it can help, you can have a look at the sources of Material-UI around how the library solves this issue.

[craigpalermo]

@oliviertassinari Thanks, that's an excellent suggestion! It seems like Material's modal has the behavior we want (at least in the context of their docs site), so I'll have to see what we can do to get closer to their implementation.