Error when trying to parse es6 js file with import statement

This is the error when parsing [this](https://github.com/seveves/vis/blob/master/lib/network/modules/Clustering.js) file using "closure2ts Clustering.js Clustering.d.ts". Of course this happens with every file containing import statements :)

> C:\Users\sevef\Code\vis\lib\network\modules>closure2ts Clustering.js Clustering.d.ts
>
> C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:3385
> throw error;
> ^
> Error: Line 2: Unexpected token
> at ErrorHandler.constructError (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:3390:22)
> at ErrorHandler.createError (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:3408:27)
> at Parser.unexpectedTokenError (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:542:39)
> at Parser.tolerateUnexpectedToken (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:555:42)
> at Parser.parseStatementListItem (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:1801:31)
> at Parser.parseProgram (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:3054:29)
> at Object.parse (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\node_modules\esprima\dist\esprima.js:117:24)
> at Object.jsdoc (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\definition-generator\src\parser.js:412:24)
> at symbols (C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\definition-generator\src\finder.js:30:59)
> at C:\Users\sevef\AppData\Roaming\npm\node_modules\typescript-closure-tools\definition-generator\src\finder.js:70:21