title: "given version requirement is invalid" while downloading dependencies
body: <p>Following <a href="https://github.com/PistonDevelopers/Piston-Tutorials/tree/master/getting-started" rel="nofollow noreferrer">this example</a>: </p>
  
  <pre class="lang-none prettyprint-override"><code>$ cargo build --verbose
  Updating registry `https://github.com/rust-lang/crates.io-index`
  failed to parse registry's information for: wayland-client
  
  Caused by:
  the given version requirement is invalid
  </code></pre>
  
  <p>This happens on every example and builds from other repos. I am running Ubuntu 16.04 LTS and I installed Cargo and Rustc through apt.  Using versions:  rustc 1.7.0 and cargo 0.8.0.</p>
  
  <p>My Cargo.toml from the example:</p>
  
  <pre><code>[package]
  
  name = "spinning-square"
  version = "0.1.0"
  authors = [
      "TyOverby &lt;ty@pre-alpha.com&gt;",
      "Nikita Pekin &lt;contact@nikitapek.in&gt;"
  ]
  
  [[bin]]
  name = "spinning-square"
  
  [dependencies]
  piston = "0.31.1"
  piston2d-graphics = "0.21.1"
  pistoncore-glutin_window = "0.35.0"
  piston2d-opengl_graphics = "0.40.0"
  </code></pre>