Allow using names in skeletons

[0xdeadfeee]

Thanks for the plugin!
Really cool thing, but I was missing the ability to use filenames for skeleton decision
My main use-case was the "CMakeLists.txt" file, as I understood I can only really define skeleton.CMakeList.txt with my skeleton and empty skeleton.txt which would then result in plugin asking which I want for every single txt file - I find that to be suboptimal therefore I propose this:
Skeletons will be able to have filenames in them, in the following format skeleton-<name>.<subtype>.<extension>
This way I could define skeleton-CMakeLists.txt for my usecase which would automatically get expanded if the filename is CMakeLists, otherwise it would use non-named skeletons