Refactored, removed old remnants from v0.1.0, documentation added

schema.go

@@ -1,3 +1,22 @@
+/*
+Package dbschema is used to keep the SQL schema up to date.
+
+	func sqlProvider(dbName string, version int) (sql []byte, found bool) {
+		// read an SQL file and return the contents
+		return
+	}
+
+	upgrader := dbschema.NewUpgrader()
+	upgrader.SetSqlCallback(sqlProvider)
+
+	if err = upgrader.AddDatabase("127.0.0.1", 5432, "foo", "postgres", "password"); err != nil {
+		panic(err)
+	}
+
+	if err = upgrader.Run(); err != nil {
+		panic(err)
+	}
+*/
 package dbschema
 
 import (
@@ -8,6 +27,7 @@ import (
 	"database/sql"
 )
 
+// An upgrader verifies the schema for one or more databases and upgrades them if possible.
 type Upgrader struct {
 	databases map[string]Database
 	logCallback func(string, string)