linux: Fix compilation warning from dbus
Link with dbus
linux: Fix detect global menu bar

It seems that detecting the bus name "com.canonical.AppMenu.Registrar"
is the most reliable way to detect whether the appmenu is available, see
http://git.io/JmP7Yg for the discussion.
Upgrade libchromiumcontent for dbus headers
linux: Add libdbus-1-dev as requirement
Merge pull request #726 from atom/dbus-checking-menu

Fix detecting global menu bar on Ubuntu
Add libgio loader
Update libgio_loader for some APIs
linux: Set scale factor to the value in gsettings
linux: Make scale factor default to 1
linux: Also check for schema before init
Make code cleaner
linux: Don't append --force-device-scale-factor to process.argv
Merge pull request #727 from atom/high-dpi

Set DPI settings from gsettings on Linux
Bump v0.18.2.
Add API to register custom element
Add code to register <webview> tag
Schemas should be registered early
Fix js errors in webview
Make WebContents cache object template