Get commons-io from source, not binary

Fix #1

app/build.gradle

@@ -43,5 +43,5 @@ android {
 dependencies {
     compile 'com.android.support:appcompat-v7:23.4.0'
     compile files('../libs/CompareString.jar')
-    compile files('../libs/commons-io-2.4.jar')
+    compile 'commons-io:commons-io:2.4'
 }