Added libicu48 dependency
Use same viewport default (1024x768) in Xvfb conf

To match https://github.com/scrapinghub/splash/blob/master/splash/defaults.py#L10
Some install docs. See GH-71 and GH-108.
Merge branch 'master' into HAR
fix pageref type
Merge branch 'HAR' into HAR-multi-pages