message: Update information about supported rust toolchain version in the README
diff: @@ -35,10 +35,10 @@ curl https://sh.rustup.rs -sSf | sh
  Rust nightly is required to build this project.
  ```
  -rustup install nightly-2019-08-25
  -rustup default nightly-2019-08-25
  +rustup toolchain install nightly-2019-10-04
  +rustup default nightly-2019-10-04
  ```
  -Application has been tested to compile with `rustc 1.39.0-nightly (521d78407 2019-08-25)`.
  +Application has been tested to compile with `rustc 1.40.0-nightly (032a53a06 2019-10-03)`.
  **3. Install required libs**
  