Merge pull request #49 from AutoScout24/xcode6-ios8

Xcode 6 / iOS 8 needs a scaleFactor
Support testing on iPhone 6+ with @3x assets
Merge pull request #51 from yas375/iphone6-plus-support

Support testing on iPhone 6+ with @3x assets
Update .travis.yml

Run tests manually to fix CI error.
Merge branch 'master' of github.com:facebook/ios-snapshot-test-case into as24-master