Version 4.0.0

Complete rewrite of the library to backport the Android 4.0 action bar.

• The minimum supported version of Android is now 2.1 (API 7).
• New base activities are provided (e.g., SherlockActivity and
  SherlockFragmentActivity) which extend from the native activities.
• The support library sources are no longer included in the library. You must
  include android-support-v4.jar in your project separately.
• Theming now mirrors that of the native action bar through the use of multiple
  styles rather than through ab- and am-prefixed attributes in the theme.
• The action bar can be statically attached to an activity view without the
  requirement of using one of the provided base activities.