Log Message:
Updated to 2.6.2. ruby18 isn't supported. From NEWS.md:

### Bug fixes

* If you have a Rails >= 4.1 project and you are running tests using Spring,
  matchers that depend on assertions within Rails' testing layer (e.g.
  `render_template` and `route`) will no longer fail.

* Fix `permit` so that it can be used more than once in the same test.

* Revert change to `validate_uniqueness_of` made in 2.6.0 so that it no longer
  provides default values for non-primary, non-nullable columns. This approach
  was causing test failures because it makes the assumption that none of these
  columns allow only specific values, which is not true. If you get an error
  from `validate_uniqueness_of`, your best bet continues to be creating a record
  manually and calling `validate_uniqueness_of` on that instead.

### Other changes

* The majority of warnings that the gem produced have been removed. The gem
  still produces warnings under Ruby 1.9.3; we will address this in a future
  release.