readme example does not compile

[matthiaskrgr]

fn main() {
    

use cgroups_rs::*;
use cgroups_rs::cgroup_builder::*;

// Acquire a handle for the cgroup hierarchy.
let hier = cgroups_rs::hierarchies::auto();

// Use the builder pattern (see the documentation to create the control group)
//
// This creates a control group named "example" in the V1 hierarchy.
    let cg: Cgroup = CgroupBuilder::new("example")
        .cpu()
        .shares(85)
        .done()
        .build(hier);

// Now `cg` is a control group that gets 85% of the CPU time in relative to
// other control groups.

// Get a handle to the CPU controller.
let cpus: &cgroups_rs::cpu::CpuController = cg.controller_of().unwrap();
cpus.add_task(&CgroupPid::from(1234u64));

// [...]

// Finally, clean up and delete the control group.
cg.delete();

// Note that `Cgroup` does not implement `Drop` and therefore when the
// structure is dropped, the Cgroup will stay around. This is because, later
// you can then re-create the `Cgroup` using `load()`. We aren't too set on
// this behavior, so it might change in the feature. Rest assured, it will be a
// major version change.

}

error[E0308]: mismatched types
  --> src/main.rs:13:22
   |
13 |       let cg: Cgroup = CgroupBuilder::new("example")
   |  _____________------___^
   | |             |
   | |             expected due to this
14 | |         .cpu()
15 | |         .shares(85)
16 | |         .done()
17 | |         .build(hier);
   | |____________________^ expected `Cgroup`, found `Result<Cgroup, Error>`
   |
   = note: expected struct `cgroups_rs::Cgroup`
                found enum `Result<cgroups_rs::Cgroup, cgroups_rs::error::Error>`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `cg` due to previous error

cgroups-rs 0.3