Grunt aliases contained obsolete epubReadingSystem tasks, not sure how it got back there

...was moved to feature branch at this point in time: https://github.com/readium/readium-js-viewer/commit/03d96ab40b5c4b5914d7e589d66db06d8152305d#diff-2
Merge branch 'develop' into feature/firefox-addon

Conflicts:
	grunt/aliases.js