Inset and new iphone dimensions for safearea

v1.0.0-beta.23-inset-safearea

add iphonex helpers

Fix insets for iphone x and header height

v1.0.0-beta.22-insetfix

Merge branch 'master' of git://github.com/react-navigation/react-navi…

Fix insets for iphone x and header height

v1.0.0-beta.19-insetfix

fix header height in landscape and use always the inset on iphone x i…