Basic Image Upload Functionality

I have added basic image upload functionality

I have taken javascript from http://benfoster.io/blog/pagedown-markdown-editor-custom-image-dialog

And used bits of djanog-ckeditor image upload code to create this functionality.

Currently it creates a jquery ui dialogue and uses jquery ajaxuploader to upload files.

No resize functionality.

And I have removed pagedown submodule and added js directly.