Report line and offending character on errors

This will respond with the following output upon an error:

```shell
$ grunt webpack:dist
Running "webpack:dist" (webpack) task

Running "actualWebpack:dist" (actualWebpack) task
Version: webpack 1.1.8      
Asset  Size  Chunks       Chunk Names

ERROR in ./src/index.coffee
Module build failed: Error: SyntaxError: unexpected WHEN
    L15: require ['./app'], (App) -> App.create() when if that
                                                  ^

    at Object.module.exports (/Users/Kyle/Documents/www/coffee-loader/index.js:37:9)
Warning: Task "actualWebpack:dist" failed. Use --force to continue.
Error: Task "actualWebpack:dist" failed.
    at Task.<anonymous> (/Users/Kyle/Documents/www/ynab/ynab_web/node_modules/grunt/lib/util/task.js:200:15)
    at null._onTimeout (/Users/Kyle/Documents/www/ynab/ynab_web/node_modules/grunt/lib/util/task.js:236:33)
    at Timer.listOnTimeout [as ontimeout] (timers.js:110:15)

Aborted due to warnings.
```

Fixes GH-5. Cheers!