Added .gitignore with *.elc

Currently if I byte-compile scala-mode2, it will create a lot of .elc files which git currently does not ignore. If I then wish to commit patches, this is quite annoying. Even more annoyingly I wish to use scala-mode2 as a submodule of my emacs configuration and this will mean that my elisp repo will also show that scala-mode2 has changed. I can't then commit this change and use it across multiple machines without maintaining a fork and keeping that up to date with upstream would be rather a pain.