Bump version to 0.5.7

AndroidManifest.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
       package="org.thoughtcrime.securesms"
-      android:versionCode="20"
-      android:versionName="0.5.6">
+      android:versionCode="21"
+      android:versionName="0.5.7">
     <application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="false">
         <activity android:name=".SecureSMS"
                   android:label="@string/app_name"
@@ -106,4 +106,4 @@
 <instrumentation android:name="android.test.InstrumentationTestRunner"
        android:targetPackage="org.thoughtcrime.securesms.tests" android:label="Tests for My App" />
 
-</manifest> 
+</manifest>