Gracefully handle images.

Because Grunt is running the instance as a server as opposed to a file:///, it creates issues with having images in the base directory.

While I figure out the best way to handle it, the workaround is to put your images in the _project-name_/ directory somewhere and link to those. It's confusing and messy but it works right now.

I'm either going to make simple symlink (which I'll have to wait for the new version of Yeoman to come out so I can use the spawnCommand method), make a Grunt task to do it either by copying (I don't like the duplication of data) or symlinking (I don't like this because it will do it every time the code runs which is wasteful), or I can write it directly into mdpress and submit it as a pull request.