Don't optimize method signatures out of facebook sdk, they needs them

astrid/proguard.cfg

@@ -7,7 +7,7 @@
 
 # astrid-specific
 -dontobfuscate
--keepattributes SourceFile, SourceDir, LineNumberTable, LocalVariableTable, LocalVariableTypeTable
+-keepattributes SourceFile, SourceDir, LineNumberTable, LocalVariableTable, LocalVariableTypeTable, Signature
 -keep, allowshrinking, allowoptimization class com.todoroo.**
 -keep class com.mdimension.**
 -keep class com.google.common.base.Preconditions
@@ -47,6 +47,10 @@
     *;
 }
 
+-keep class com.facebook.** {
+   *;
+}
+
 -keepclassmembers public class com.todoroo.astrid.data.* {
     *;
 }