Modules refactor

src/steps/os/mod.rs

@@ -0,0 +1,10 @@
+#[cfg(target_os = "freebsd")]
+pub mod freebsd;
+#[cfg(target_os = "linux")]
+pub mod linux;
+#[cfg(target_os = "macos")]
+pub mod macos;
+#[cfg(unix)]
+pub mod unix;
+#[cfg(target_os = "windows")]
+pub mod windows;