Rename 'finish-launching' event to 'ready',

'finish-launching' is more like a OS X message name, and in atom-shell
it means initialization has done, so 'ready' seems to be a better name
and more easy to remember.

The 'will-finish-launching' event just represents the corresponding
message on OS X and is the same with 'ready' on other platforms, so we
keep its name to indicate that it's only useful for OS X specified
code.

browser/api/lib/app.coffee

@@ -28,5 +28,8 @@ if process.platform is 'darwin'
     setBadge: bindings.dockSetBadgeText
     getBadge: bindings.dockGetBadgeText
 
+# Support old event name.
+app.once 'ready', -> app.emit 'finish-launching'
+
 # Only one App object pemitted.
 module.exports = app