Cleanup code: step 1: fix warnings.
Fix build for Rust master.
Cleanup code: step 2: style.
Cleanup code: step 3: fix warnings.
Change build system to use Cargo.

I moved all the sources to src folder.
Renamed the projet and the binary to scmrun du to the impossibility to use
a dot in a project name with Cargo.
Fix build for Rust master.
Update README.md.
Merge pull request #1 from darnuria/cargotify

Change build system to use Cargo.