Version bump

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/build.gradle

@@ -17,8 +17,8 @@ android {
         applicationId 'com.wireguard.android'
         minSdkVersion 21
         targetSdkVersion 28
-        versionCode 439
-        versionName '0.0.20180826'
+        versionCode 440
+        versionName '0.0.20181001'
         buildConfigField 'int', 'MIN_SDK_VERSION', "$minSdkVersion.apiLevel"
     }
     // If the keystore file exists