Add --stdout option / redirect error messages to stderr #79
I added an option to take output to stdout. This is my first attempt to write Rust code other than hello world, so I believe it could be not-so-much-idiomatic ;) Please take your time to tell me if there's anything to fix!
Also, I redirected error messages to stderr to prevent error messages to be written to stdout. I needed this option because I wanted to replace svgo with svgcleaner, using stream interface in Node.
Looks good, but there are few problems:
As for code itself - I've added few comments.