message: Update README.md
  Correct the version string in the readme.
diff: @@ -67,7 +67,7 @@ crates.io. To include it in your project, just add the dependency
  line to your `Cargo.toml` file:
  ```text
  -ggez = "0.5"
  +ggez = "0.5.0-rc.2"
  ```
  ggez consists of three main parts: A `Context` object which
  