[RFC] Adding Redshift support

[Alexandre Bourget]

I'm about to add Redshift support to goose.

I found goose to be the best fit for my project. I wanted: * a simple executable, and simple dependencies (no gorp) * timestamp based migration files * support for SQL files, and maybe .go programs.. which is neat * reuse of lib for test scripts * a nice layout for the migrations table * simple extensibility for Redshift (like not relying on a third-party lib for DB abstraction). * config file based

the only thing I'm less satisfied is with the error logging... I often don,t know from which part I'm getting an error, since most of the errors aren,t prefixed with their context.. I get a weird Redshift error, but I'm not sure if it occurs when trying to query for the migrations table, when it's trying to create it, etc.. if that's okay.. I'd like to improve the prefixes for errors when they bubble up

Also, for testing, I'd like to be able to mute, or mock the textual output of the errors or process.. so maybe having an abstraction for all the logging that occurs, or log.Fatal() calls. Do you think I could rework that while doing the Redshift things ?