Initialize ProtocolHandlerInstaller after initializing Config

This allows it to correctly read `core.uriHandlerRegistration` and
avoids popping the notification even if set to 'never'.

Fixes atom#16201

Port fix to protocol handler 'no never' not working from master/1.24

Remove the texteditor isModified/isReadOnly handling intended for uns…

…avable edit buffers as causes issues with vim-mode-plus

Try the deprecated travis image to resolve python version error

We probably need to fix this on master, but for a release branch it
seems ok to defer that.

1.24.0-beta0

1.23.0

⬆️ autocomplete-plus@2.37.5

⬆️ autocomplete-plus

⬆️ github@0.8.2

1.22.0