Vendor dependencies

Let's see how I like this workflow.

vendor/procfs/examples/pressure.rs

@@ -0,0 +1,7 @@
+/// A basic example of /proc/pressure/ usage.
+
+fn main() {
+    println!("memory pressure: {:#?}", procfs::MemoryPressure::new());
+    println!("cpu pressure: {:#?}", procfs::CpuPressure::new());
+    println!("io pressure: {:#?}", procfs::IoPressure::new());
+}