nimble file should not use cligen@#head

[c-blake]

head is just one snapshot in time and pollutes the nimble dir for other packages.

Also, you should change create to the qualified cli.create in github_release.nim. (You might want to do that for all the procs, but create collides with something from system.nim now.)

Cheers.

[kdheepak]

Good point. I'll change this.

[c-blake]

For what it's worth, even the sdl2_nim author who's been using Nim since 2013 thought a #head version meant "always updated" rather than "never updated unless an end user rm -rfs the foo-#head in pkgs/". This is one of a few ways in which nimble seems mis-optimized.