Rename show and menu class names in menu element that are likely to collide with styles that are already in use.

[ouromoros]

Hi, I'm myself a front-end noobie and I came into this problem today.

The problem is that my website already has css styles for class show and menu, which caused the related spotlight UIs (the navigate menu) to behave in an odd way.

Today it took me a lot of time to track down this problem. I ended up having to use css-selectors like #spotlight.menu to explicitly disable the errorneous styles in order to get the UIs working.

I think we'd better use class names like spotlight-show instead of show to avoid accidents like this. Since spotlight aims to be the most easy to integrate js gallery, it's important to avoid this kind of unintended behavior that would surprise users.