Prepare for release: v0.2.0

Fixes
- Properly close database when finishing

*Breaking change*
- Change migration files and commands from `up` to `migrate` and
  `down` to `rollback`

shard.yml

@@ -1,5 +1,5 @@
 name: drift
-version: 0.1.1
+version: 0.2.0
 license: Apache-2.0
 crystal: ">= 1.4.0, < 2.0.0"
 authors: