Removed IDEA plugin, and add application plugin.
Updated the Gradle wrapper.
Added .local.vimrc and .swp files to gitignore.
Added headless detection and filechooser field.
Headless detection will ensure that you have a display while running the IDE, if not, it will throw a java.awt.HeadlessException. I also stored the JFileChooser as a field, rather than disposing it each time from a open/save. It saves you time from having to rebrowse to a different folder.
Changed the README up a little bit to be better worded.