Add Gruntjs for development

Hi Syamil,

Based on my perspective, using [Gruntjs](http://gruntjs.com/ "GruntJs") for development will be more portable between contributor in the future, just like [WordPress did](https://core.trac.wordpress.org/browser/trunk/Gruntfile.js "WordPress GruntJs"). So I add some simple configuration to do some simple task such as generate `.pot` file, minify `css`, `js`, etc.

Second, I continuing @luizrw great works by updating the text domain, fix some translation strings and generate `.pot` file (Theme and plugin is kinda different on how they load the translation file). The new translation file name should be:  ( e.g `aqpb-ms_MY.mo`, `aqpb-pt_BR.mo`, `aqpb-id_ID.mo`, etc).

Thanks