Allow this to work with page caching

[MSchmidt]

The banner is shown/hidden while rendering the page in Rails. I think it's preferable as plain javascript solution that would work with page caching or similar activated. Meaning the banner should always be rendered by rails (but set to hidden). Then we check for the cookie via javascript and unhide the banner when necessary.

[strehlst]

We unfortunately needed to step back from using this gem due to the incompatibility with page caching as stated by @MSchmidt Anything planned?

[gabskoro]

We started also having some other problems with the current approach (#55 (comment)), so It makes sense to evaluate the idea, will definitely take a look, tnx :)