[FIX #46] Pass formatter and formattersDirectory options to Linter object

[dpopescu]

This update will pass the formatter and formattersDirectory to tslint's Linter object.

Example (webpack.config.js):

The configuration below will generate the correct report format.

tslint: {
        formatter: 'checkstyle',
        fileOutput: {
            dir: './reports/checkstyle',
            ext: 'xml',
            clean: true,
            header: '<?xml version="1.0" encoding="utf-8"?>\n<checkstyle version="5.7">',
            footer: '</checkstyle>'
        }
    }