Check all file modes, not just writable
Check all file modes, not just writable

We run a `chmod g+rwx` to set read, write and execute permissions but only use
`File.writable?` to detect which directories need this. Since we are setting
read and execute permissions, we should also use `File.readable?` and
`File.executable?`.

princeofdarkness76/homebrew,princeofdarkness76/homebrew,princeofdarkness76/homebrew,princeofdarkness76/homebrew