Add MySql support

[Ranger2959]

After reading a bunch about StackOverflow's DB migration process, I started writing one based on the blog posts I could find, until I found out about this repo. I'm mainly using MySql in my projects now, so I wanted a version of this migrator for MySql, so that's what this pull request is.

Let me know what you think and i'm open to any suggestions you have about the implementation.

[bretcope]

Hey, I haven't meant to ignore this for so long. I just have no time to maintain this library at the moment. I started a complete redesign at one point because I wasn't particularly happy with the initial design, but I ran out of free time. It's different enough that if I ever finish it, I probably shouldn't even call it Mayflower.

So, in essence, I'm saying I don't have time to work on this library, and if I did, I'd be working on a replacement, instead of improving the existing code. If you're interested enough, I could make you a maintainer.

At a glance, your changes look good, except for how you deleted the sample SQL Server files. There's also a part of me that feels like a solution which was extensible, and would result in different libraries for different db providers would probably be better than pulling every database in as a dependency. However, that is also more work, and I don't have the time to care much at this point.