Micrate Versions Save

• Fixes N timestamps collisions by using .map_with_index (see changes)

• Fixes critical bug related to version mismatch between filename timestamps and table micrate_db_version on database. (see changes)

• Bugfix release to be v0.3.0 compatible.
• Fix to group by index without missing versions with same timestamp.
• Fixes our Travis CI failures.
• Fixes definitively #32 #31 and https://github.com/amberframework/amber/pull/775
• Still requires to be published on master to create micrate version v0.4.0 (breaking changes)

Use Crystal DB API. Adds support for MySQL and SQlite3 besides Postgres.

Logging/output improvements

Fixes in CLI exit codes.

Micrate now checks if migrations were added out of order to the migrations directory and warns the user. (See #2)