Incorrect parsing for interpolation in a directive

[firehist]

Copy from angular-translate/grunt-angular-translate#72.
cc @stefan2718

There is incorrect parsing in the case of interpolating the translation ID inside a directive. The following line is pulled into the language file like so:

File.jade:

span(translate="{{$ctrl.cardData.comparisonString}}") {{$ctrl.cardData.comparisonString}}

en.json:

"{{$ctrl": {
    "cardData": {
        "comparisonString}}": ""
     }
}