* Update make targets:
* `make dev` now shows a message indicating the new commands
* `make build` builds the binary into bin/
* `make install` will subsequently `mv` (not copy) the binary into
GOPATH/bin
The reason for the `mv` is that M1 Macs seem to get pretty unhappy about
executing a copied binary if it's been modified, so an initial binary is
fine, then after changing and recompiling the command keeps getting
killed.
* Make the 'make install' text more clear