Minor changes in Estonian translation
Merge pull request #4014 from stevekr/master

Minor changes in Estonian translation
Fix typo [skip ci]
Imagick image can not be converted to string on HHVM

made it consistent with the GD function.

See also https://github.com/yiisoft/yii/pull/3406
Merge pull request #4015 from klevron/temp

Fix typo in input-validation.md guide [skip ci]