Ensure reload works even when the socket directory does not exist

[milk1000cc]

I use this gem with puma-dev by adding export SERVER_PROCESS=1 to .pumaenv (#31) .

In this setup, the tmp/sockets directory is not created, which causes the gem to not work properly.

(Note: When running rails s, the directory is automatically created.)

I have modified the code to automatically create the socket directory if it does not exist.

[igorkasyanchuk]

thanks