Using alternative parsers

[justin-lau]

The problem: the linter API this plugin is using right now does not accept alternative parsers. I'm using eslint-config-airbnb that uses babel-eslint as its parser. With this plugin the parser option set in the config file is not consumed, and therefore complains about some of the syntax I use with Babel.

I tried using the CLIEngine API directly in my gobblefile with built-in formatter, and it worked perfectly with eslint-config-airbnb.

I was going to create a PR but I found that the CLIEngine API was implemented long before this plugin. It keeps it me thinking there may be some good reasons behind this.

[julienw]

I proposed a PR in #2 about this.