Adding mixpanel lib to the app.

Creates a single mixpanel instance on the Application.
Refs #288.
Abstract stats wrangling into its own class.
Adds Quantcast lib.

WPMobileStatsUtil is patterened off the iOS version.
Corrects argument order. Adds documentation.
Adds const for quickphoto event.
Adds stats tracking for posts.

Updates some consts to represent properties instead of events.
Adds new properties and events.
Refs #288
Fix #322: add a _visit security settings_ button that open a browser in WordPress.com->Settings->Security to create an app specific password when 2FA is enabled and master password entered
Merge branch 'feature/nux-improvements' into issue/322-better-ui-2fa-detected
Use onTouchListener instead of onClickListener.
Fixes the constant used for mixpanel token.
Flush events when tracking saved properties. We typically do this when an activity is destroyed so its a convenient way to sync.
Merge branch 'develop' of https://github.com/wordpress-mobile/WordPress-Android into feature/mixpanel
Merge branch 'develop' into issue/322-better-ui-2fa-detected

Conflicts:
	src/org/wordpress/android/ui/accounts/TutorialActivity.java
Open Notifications links in webview
Do not show "sign out" and "settings" menus in the webview
Use constants when setting bundle extra items.
App now sends a broadcast upon signout which is received by WPActionBarActivity.

WPActionBarActivity calls onSignout() when this broadcast is received, so descendants can do activity-specific cleanup when the user signs out.

NativeReaderActivity relies on this to clear the post fragment when the user signs out (otherwise, the previously displayed posts will continue to show if the user logs back in)
Merge pull request #374 from wordpress-mobile/issue/338-clear-reader-on-signout

Fix for #338 (clear reader on signout)
Merge pull request #366 from wordpress-mobile/issue/322-better-ui-2fa-detected

Fix #322: Add "visit security settings" button when master password is entered and 2 factor authentication detected
Added tap to reply to a comment (previously used long-press to reply, which wasn't obvious)
Hide zoom buttons, and add the "up" button to the ActionBar.
Add the "custom" progress/loading indicator we already use in others webview within this app.