Adding an overflow hidden and a title to the nav module names to prevent...

... the line breaking when the module name is too big,

The overflow: hidden was to stop the line breaking and the title is to improve the readability of partially hidden module names. A small change but a nice aesthetical improvement, imho! :)

P.S.: This is my first pull request and I'm not familiar with common conventions/policies. I tried looking for some sort of wiki on this project on how to contribute but I couldn't find anything. Apologies for any mistakes in advance!