added navigation-top-stories test
updated top stories test
refactored section-front test
added tasks to Gruntfile
Merge remote-tracking branch 'remotes/origin/master' into update-casper-tests
Resolving conflict
Merge remote-tracking branch 'origin/master' into update-casper-tests

Conflicts:
	Gruntfile.js
Merge branch 'master' of https://github.com/guardian/frontend into update-casper-tests
fixed indentation
Merge pull request #1540 from guardian/update-casper-tests

Update casper tests