Bump up minimum supported Android version, add ActionBarSherlock dep.

The minimum supported Android device is now 2.2 (Froyo).
And we're embracing the ActionBarSherlock madness.

AndroidManifest.xml

@@ -3,7 +3,13 @@
       package="org.thoughtcrime.securesms"
       android:versionCode="21"
       android:versionName="0.5.7">
-    <application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="false">
+
+    <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="14"/>
+
+    <application android:icon="@drawable/icon"
+                 android:label="@string/app_name"
+                 android:theme="@style/Theme.Sherlock.Light.DarkActionBar">
+
         <activity android:name=".SecureSMS"
                   android:label="@string/app_name"
                   android:launchMode="singleTask"
@@ -78,8 +84,6 @@
        <uses-library android:name="android.test.runner" />
 </application>
 
-<uses-sdk android:minSdkVersion="4" />
-
 <permission android:name="org.thoughtcrime.securesms.ACCESS_SECRETS"
             android:label="Access to TextSecure Secrets"
             android:protectionLevel="signature" />