ELPA installation

This commit make `yasnippet-java-mode` installable from [MELPA](http://melpa.milkbox.net/).

`java-snnippets.el`will be able to automatically load snippets for java-mode without configuration.

For information about this fix, Quoting [Packaging-Basics](http://www.gnu.org/software/emacs/manual/html_node/elisp/Packaging-Basics.html):

> Emacs then searches every Lisp file in the content directory for autoload magic comments (see Autoload). These autoload definitions are saved to a file named name-autoloads.el in the content directory. They are typically used to autoload the principal user commands defined in the package, but they can also perform other tasks, such as adding an element to auto-mode-alist (see Auto Major Mode).