Add the ability to define a specific version of composer to use on the server

[kodie]

Currently, you're required to install Composer, globally, on the server yourself manually. We've run into issues with some older websites that require an older version of Composer. We've also ran into issues where Composer would auto-update itself and cause issues.

I think it would be nice to be able to define a Composer version in your config.yml file and have WP-Deployer download it on the server and use that local copy.