ecs - one line install script

[ecshreve]

This script downloads the latest release of the run binary from GitHub and extracts it to the working directory.

Addresses #94

• wrap in main() function and call main at the end of the file
• pulled OS and ARCH into variables, reuse them in success output
• output the version information on successful installation
• update readme

[amonks]

oops: I said "fftm", but I don't think you can actually hit the merge button. If you can't, just comment :)

[amonks]

woohoo! 🚢