Use rake-compiler to make development a bit easier

[ankane]

Just a suggestion, so feel free to close without comment if there's not any interest. This should make development a bit more standard as well as easier for Mac users (I believe it can eliminate the need for the custom setup scripts).

Edit - Here's the link: https://github.com/rake-compiler/rake-compiler

bundle exec rake compile

On Mac, the current setup.rb script doesn't return any errors, but doesn't appear to compile the extension.

ruby setup.rb compile
(ruby 2.7.1 x86_64-darwin18)

- - COMPILE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 

Instead, my workflow as been:

ruby ext/numo/narray/extconf.rb
make
cp narray.bundle lib/numo/narray.bundle

[ankane]

Thanks @masa16!