Updated vimrc

-Added settings to make unite work more like ctrlp.
-Added setting ttyfast which improves redrawing.
-Added setting hidden which allows you to edit other files
 without having the need to save the current file.
-Added setting to not create backup files when editing in vim.
-Allowed syntastic to also run on html and css files.
-Source vim-markdown only on markdown files.
-Reformatted vimrc.