Migrations - docs should make clear that execution order is important.

[gdaniels]

Hey there - just checking out your neat little library. Right now your migrations are controlled entirely by the size and order of the Sprinkles.mMigrations list, which is determined by the code that creates them. Although your README makes clear that you shouldn't change a migration after it's in production, you should maybe also point out that you should a) never change the order of migrations in your code, and b) only add new migrations at the end?

[emilsjolander]

yeah, i'm reworking how migrations work and i will keep this in mind when writing the new documentation :+1: