Added a proguard file that should fix a crash on Android 4.2 for Samsung

Also reduces the size of the APK.

build.gradle

@@ -40,6 +40,10 @@ android {
         checkReleaseBuilds false
     }
     buildTypes {
+        release {
+            minifyEnabled true
+            proguardFiles getDefaultProguardFile('proguard-android.txt'),'proguard-rules.pro'
+        }
     }
 }
 
@@ -53,6 +57,7 @@ dependencies {
     compile 'org.apache.sshd:sshd-core:0.8.0'
     compile 'org.bouncycastle:bcprov-jdk16:1.46'
 
+
     androidTestCompile 'org.mockito:mockito-core:1.10.19'
 
     // Because mockito has some problems with dex environment

proguard-rules.pro

@@ -0,0 +1,28 @@
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in {SDKHOME}/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Allow obfuscation of android.support.v7.internal.view.menu.**
+# to avoid problem on Samsung 4.2.2 devices with appcompat v21
+# see https://code.google.com/p/android/issues/detail?id=78377
+-keep class !android.support.v7.internal.view.menu.**,** {*;}
+
+-dontwarn org.apache.sshd.**
+-dontwarn org.apache.mina.**
+-dontwarn org.bouncycastle.**
+-dontwarn org.slf4j.**
+