Build: Rearrange grunt/npm tasks into a build/dist/test pattern

Ref 76df9e4e389d80bff410a9e5f08b848de1d21a2f
Ref https://github.com/jquery/jquery/pull/1949#discussion_r22042517
I've just noticed this will most likely not work on Windows unless run via Bash. This also affects current build script definition.

cc @dmethvin