Modal Fixes for WordPress 3.8

Already sent a bad pull request. Submitting this better one.

Fixes issue where a long modal (exclude) would show underneath the WP admin bar. See https://cloudup.com/cndYCTTfh0M

Now the modal always follows 85% of the height and doesn't auto resize underneath the WP Admin bar. See https://cloudup.com/i0gZg1ZjDOU

The only questionable item may be the long scrolling on the exclude modal. When leaving the file list an `overflow:scroll` it was hard to scroll the modal and scroll the modal list, so I opted to remove `overflow:scroll`.

Also fixes the issue where long paths (see https://cloudup.com/cyCazJsze9k) would not `word-wrap` correctly.