Fix build for new rustc version

I upgraded my Rust compiler today:
```rustc 0.12.0-pre (02f9fd87e 2014-08-15 15:46:17 +0000)```

After doing that, I got a few build warnings/errors which I fixed by:
 - Using indexing (i.e. obj[key]) instead of deprecated get function
 - Using slice_from instead of deprecated tailn function
 - Passing Duration instead of u64 to sleep function after api change