Added option to include full domain name for js, css, and image files

1) This PR adds a "host_name" config variable to the main settings.

When set to a domain name, it will prepend JS and CSS tag sources with the specified domain name. It will also add the domain name to images specified in CSS files.

By specifying this option with an environment variable, assets can be accessed locally for development environments and accessed through a CDN in production environments. For instance: using assetpack in conjunction with the active_sync gem to deploy assets to an Amazon S3 bucket.

2) Also added a force UTF-8 console output. When running rake tasks, long filenames were being output as ASCII and the rake task would fail.