Should throw exception when variable names doesn't match

[MrOrz]

When resolving po files containing errors in variable names, babel plugin should throw an error.

For instance:

msgid "Created at ${ createdAtStr }"
msgstr "作成日 ${ cratedAtStr }"  # typo here

Currently the po file above will cause ReferenceError late at runtime.

[MrOrz]

After digging in the code, I found that it would be easier to check if all expressions in the source string appears in the localized strings.

This would stops translators from deliberately omitting expressions. However, I personally did not have such use case, so maybe I will just implement this way.

[AlexMost]

makes sense

[oleksandr-kuzmenko]

👍

[vharitonsky]

Also, it would be cool to check if no new expressions were introduced. This way will prevent copy/paste errors.

[AlexMost]

works in 0.5.6