Extract translations

(Consolidated changes from #10 and #11).

This way if an application does not need a particular translation, the file can just be omitted and the overall file size will be reduced.

Adding new translations becomes easier this way, too.

Many modern web frameworks support asset file bundling (concatenation and minification) and multiple files should not be an issue.

If this is accepted, I will send a new PR with a Bulgarian translation.

The minified version of the script is not updated. I propose we update it later, after all changes have been merged.