Calculate where to scroll to based off the position in the div

Also, only scroll if not currently visible.
Merge pull request #871 from simonwelsh/3.1-scroll

Calculate where to scroll to based off the position in the div
Add an extension hook for customising site tree hints.
Merge pull request #873 from ajshort/pull-2

Add an extension hook for customising site tree hints.
Avoid encoded HTML breadcrumbs
FIX Remove invalid single quote
Merge pull request #876 from cieszak/3.1

FIX Remove invalid single quote
Behat travis tests
Merge remote-tracking branch 'origin/3.1'

Conflicts:
	.travis.yml