Add OS specific modules

src/macos.rs

@@ -0,0 +1,13 @@
+use super::utils::Check;
+use failure;
+use std::process::Command;
+
+pub fn upgrade_macos() -> Result<(), failure::Error> {
+    Command::new("softwareupdate")
+        .args(&["--install", "--all"])
+        .spawn()?
+        .wait()?
+        .check()?;
+
+    Ok(())
+}