Added support for Key-Value JSON Format

Recently Transifex added a support for "Key-Value-JSON" format and we thought that i18n-abide should also have that file support because it will be very useful for anyone who wants to localize their app using .json file format.

We have added a support for "key":"value" JSON type to the i18n-abide, and now the option in the type can be "key-value-json"