Unfortunately this is one of the places where Linux really doesn't have any good options. While there are definitely raw capture options for Linux, there isn't anything as nice as Screen Studio or Screen Flow or Camtasia for quick, short videos with basic editing.
I work for https://www.canvid.com, and we recently released a beta version of our product, which is similar to Screen Studio but designed for Windows. If we see enough interest, we may even release a Linux version around Q3.