validate json for translations
flatten hash option for zendesk i18n format
remove extra whitespaces
refactor default value for target key
can use target_key to imply is_i18n_format
less restrict with json gem version
make spec description clearer
use integer to compare times to fix the precision issue.
refactor validations.
Merge pull request #31 from zendesk/likun/validate_translation_json

Likun/validate translation json