Remove :github deployment option

github has/will discontinue their uploads API: https://github.com/blog/1302-goodbye-uploads

(This sucks so much :( )

The upside is, without the `net-github-upload` dependency (and indirectly `json`), one can actually install releasy on Windows without the compiler kit. I am not sure if my changes all make sense - would it be better to use `:rsync` instead of `:local` in all the examples/tests? Is `:local` the default? (I suspect it is)