Insert version to dist files on release

It's quite common (if not de facto standard) to have the version in the
file so this is a Good Thing!

> ./release 1.2.3
=>
dist/Bacon.js:
...
Bacon.version = '1.2.3';
...

Same for the minified file.
Merge pull request #282 from mileskin/version-in-dist-files

Insert version to dist files on release