Retrigger event after package module is activated

The event that triggers the package module to be activated is
now retriggered after the package module is initialized but without
any previously registered handlers. Instead only the handlers registered
by the package module will be triggered.  The prior event handlers are then
restored after the event is retriggered.

This allows package modules to bind event handlers during initialization
that will be triggered by the same event that caused the package module
intialization to occur.  This simplifies the common case of having the same
event cause a package module to initialize and attach.

spec/app/atom-package-spec.coffee

@@ -0,0 +1,36 @@
+RootView = require 'root-view'
+AtomPackage = require 'atom-package'
+fs = require 'fs'
+
+describe "AtomPackage", ->
+  describe ".load()", ->
+    [packageMainModule, pack, rootView] = []
+    beforeEach ->
+      rootView = new RootView(fixturesProject.getPath())
+      pack = new AtomPackage(fs.resolve(config.packageDirPaths..., 'package-with-activation-events'))
+      packageMainModule = require 'fixtures/packages/package-with-activation-events/main'
+      spyOn(packageMainModule, 'activate').andCallThrough()
+      pack.load()
+
+    afterEach ->
+      rootView.deactivate()
+
+    describe "when the package metadata includes activation events", ->
+      it "defers activating the package until an activation event bubbles to the root view", ->
+        expect(packageMainModule.activate).not.toHaveBeenCalled()
+        rootView.trigger 'activation-event'
+        expect(packageMainModule.activate).toHaveBeenCalled()
+
+      it "triggers the activation event on all handlers registered during activation", ->
+        rootView.open('sample.js')
+        editor = rootView.getActiveEditor()
+        eventHandler = jasmine.createSpy("activation-event")
+        editor.command 'activation-event', eventHandler
+        editor.trigger 'activation-event'
+        expect(packageMainModule.activate.callCount).toBe 1
+        expect(packageMainModule.activationEventCallCount).toBe 1
+        expect(eventHandler.callCount).toBe 1
+        editor.trigger 'activation-event'
+        expect(packageMainModule.activationEventCallCount).toBe 2
+        expect(eventHandler.callCount).toBe 2
+        expect(packageMainModule.activate.callCount).toBe 1