add proguard configure

[captain-miao]

Warning:com.cocosw.favor.MethodInfo: can't find referenced class com.f2prateek.rx.preferences.RxSharedPreferences
Warning:com.cocosw.favor.MethodInfo: can't find referenced class com.f2prateek.rx.preferences.Preference
Warning:com.cocosw.favor.MethodInfo: can't find referenced class com.f2prateek.rx.preferences.RxSharedPreferences
Warning:there were 10 unresolved references to classes or interfaces.
         You may need to add missing library jars or update their versions.
         If your code works fine without the missing classes, you can suppress
         the warnings with '-dontwarn' options.
         (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
Exception while processing task 
java.io.IOException: Please correct the above warnings first.

my proguard.txt (it's working)

# favor
-dontwarn com.cocosw.favor.** { *; }
-keep class com.cocosw.favor.** { *; }

[soarcn]

Good job, thanks mate!